cold rad

[PaulRB]

I have 1 cold rad in a downstairs cloakroom.
I have flushed it, tested the valves ( not trv ) and connected a hose from the o/side tap to each valve to blast any air-locks.
I have turned off all other rads and it still won't work.
I have replaced rad with a length of 15mm pipe and the pipe gets hot immediately! Put a new rad back on and it works for 2/3 days then fails.
If I draw 1/2 a bucket from the return pipe, hot water is drawn thru the flow pipe and the rad works for 2/3 days.
I know it could be a blockage, either air or sludge, but how come I can always draw hot water thru if I drain from the return pipe?
It seems as if there is something stopping the free flow thru the system which I can by-pass by encouraging the flow when draining.
I would be interested in advice as to what should be my next step.
Someone must have come across this before!!
Thanks

 

[Leadbetter]

Take the rad outside and blast cold mains through it with an house pipe, is it an old system / old rad?

 

[PaulRB]

Take the rad outside and blast cold mains through it with an house pipe, is it an old system / old rad?

Thanks for the reply.
Did that with old rad but made no difference.
Put a length of 15mm pipe between valves and hot flowed as normal so thought it must be the old rad.
Bought new rad and installed and it got hot immediately, worked for 2/3 days and then packed up.
I've been told it could be air building up over 2/3 days and I thought of putting in an automatic release valve but I'm not sure where in the flow pipe I'd put it!
Frustrating because it works every time with the 15mm pipe and that's just a small rad!!!

 

[jase158]

try flushing out with hose again, could be that the sludge is building up in this rad, Automatic air valve would look a bit weird coming from radiator. Can get automatic bleed valves for radiator I think. have you tried bleeding radiator?

 

[PaulRB]

try flushing out with hose again, could be that the sludge is building up in this rad, Automatic air valve would look a bit weird coming from radiator. Can get automatic bleed valves for radiator I think. have you tried bleeding radiator?

Yeah I've bled the rad and the automatic valve was to go in the pipework in the ceiling ( the highest point ).
I've now had a mate suggest its not sludge or air but a "cold water barrier" stopping the hot water getting thru.
He's suggested turning the pump round the other way to see if it dislodges the cold water. Don't know if there are consequences doing that but I can see where he's coming from.
It's so frustrating because if I take off the rad and replace it with 15mm pipe the pipe gets hot immediately!!!
I'm wondering whether to put a piece of pipe between the flow and return pipes, with a valve in, below the rad. In effect, short-circuiting the rad.Then when the pipe gets hot, turn off the valve in the pipe so the hot water has to go thru the rad.
Seems like a lot of trouble but I'm beginning to clutch at straws.!!!

 

[AWheating]

what type of system is it? what is the water in the system like? is the radiator near/far away from pump? is the system balanced correctly? what pump do you have and is it set on max?

sounds like air lock/problem.

 

[fuzzy]

if valves work, no air, rad clear it is circulation fault, is it 2 pipe system, balanced properly etc, check all connections and valves and then shut down ther rads to try to force round, if it goes round u need to balnce

 

[PaulRB]

what type of system is it? what is the water in the system like? is the radiator near/far away from pump? is the system balanced correctly? what pump do you have and is it set on max?

sounds like air lock/problem.

Gravity fed open vented system.
Ignore balancing because if I turn off all other rads, it still doesn't get hot!
Pump is new and identical to old pump, set to max.
Water in system is ok, fernox added and nice and clean when I drain some.
I know it seems like an air-lock but I don't understand why hot water comes thru ok when I remove rad and replace with 15mm pipe!
I like the idea that it could be a "cold water barrier" stopping the hot coming thru because I don't detect any signs of air when draining it. Also, the rad works for 2/3 days until the water in the pipe feeding it gets cold again.
Is there a problem with turning the pump around ( even for a short time ) so reversing the flow in the system, to see if it works by having the hot water coming thru the "return" pipe and pushing the cold water ahead of it in the " flow" pipe?
The TRV's I have are bi-directional so I can't see a problem there.
Thanks
?

 

[PaulRB]

if valves work, no air, rad clear it is circulation fault, is it 2 pipe system, balanced properly etc, check all connections and valves and then shut down ther rads to try to force round, if it goes round u need to balnce

New valves and pump.
Agree with circulation problem, now I need to solve it!
2 pipe system.
Would turning the pump round and reversing the flow be ok?
Thanks

 

[fuzzy]

bi directional trvs can still stick in off position

dont turn pump round shut off other rads and see if it gets round

 

[Halesowen1]

Where does your friend suggest this cold water is??

Is the system 15mm to rads or microbore? has this rad been joined onto existing system?
It sounds like a problem with the pipework, either a long draw off to the rad or it has been bent, squashed causing a restriction of flow.

 

[PaulRB]

bi directional trvs can still stick in off position

dont turn pump round shut off other rads and see if it gets round[/

Thanks, tried that, no luck.
Been told to turn pump down as it might be pushing hot water past the joint before it has a chance to enter pipe.
Gonna try that now.

Also, I will try putting in an automatic bleed valve in pipe at highest point, in case it is an air-lock.
Running out of ideas. Hoped someone else had come across a similar problem.

Thanks

 

[PaulRB]

Where does your friend suggest this cold water is??

Is the system 15mm to rads or microbore? has this rad been joined onto existing system?
It sounds like a problem with the pipework, either a long draw off to the rad or it has been bent, squashed causing a restriction of flow.

15mm.
The pipe run looks to be quite long. I can't see it all the way because it passes over a wall about 4 feet away.
The pipe is under the floor at 1st floor level, it then drops vertically to a rad in a downstairs cloakroom.
We think the cold water is in the long horizontal run below the floorboards.
I don't think its an air lock, but just in case, I'm going to drain down the system and fit an automatic air vent in the pipe because there's nothing to lose.
I've turned off all the other rads and felt the 2 pipes ( flow + return ) to see if they warm up.
The flow pipe remains stone cold + the return warms up slowly ( I think its just the water flowing thru the system gradually heating up the water in the pipe from the other end )
When I drain off 4 pints from the drain valve in the return pipe, the flow pipe gets proper hot and the rad works for 2/3 days.
Its as if the drained water is replaced by the cold water in the flow pipe, closely followed by the blocked hot water.
Then when the system cools, the cold water blocks the hot again.
It's an existing rad ( now replaced with a new one ) that worked fine for 18 years. Coincidentally, I drained the system down to replace a bathroom rad with a towel rad, and that's about the time it stopped working.
No damage to pipework.

Thanks

 

[fuzzy]

its not a 1 pipe system so dont see how it can pump past the rad? youve tried shutting down all other rads and it didnt work but youve pulled it through return and it does? youve altered the towel rad and it stopped working? this is puzzling? is there a trv on the towel rad? is the rad linked from/to the towel rad? could it be the trv shuts down both rads? this could be so if piped wrong

is there a cylinder on the system?

 

[Halesowen1]

I still reckon it is a badly balanced system.
You have definitely tuned off all the other rads? Do the rads have TRV's fitted?
Seen a similar problem dozens of times and 99% are badly balanced systems due to dodgy pipework and long runs, the other 1% is due to a blockage causes mainly by bent or squashed pipes.
The way I would be doing this is to make sure every rad is off at the lockshield valve not TRV, including hall rad if its got 2 x Lockshields. This almost always sends water to cold rad, then you need to balance the system accordingly. Just opening them all back up will not sort the problem out.
It could be air gradually building up and blocking it up, air will always rise to the top so the thing to look for is where the pipe goes up over something then back down. imagine the pipe going over a door frame. This could happen if a new pump has been replaced, the old pump may have been powerfull enough to keep pushing the air around the system.

 

[fuzzy]

yes the smart money is on badly balanced which can be enhanced by badly piped

but if he has shut off all the other rads?

 

[PaulRB]

bi directional trvs can still stick in off position

dont turn pump round shut off other rads and see if it gets round

Done that and flow pipe still doesn't get hot.
Seems like I need to drain water from the return pipe just to encourage the hot to come thru the flow pipe.
Once the rad heats up it stays working until the system shuts off + the water in the pipes cool down. Then I need to drain water to get it started again.
Gonna try draining down and taking out a piece of the flow pipe,( as high as I can ) replacing it with a "T", and fitting an air bleed valve on the arm of the "T". Just to satisfy myself that it's not an air-lock.
I've also tried turning down the pump in hope that a lesser force will give the hot water more chance of entering the flow pipe,( rather than by-passing it ) but that hasn't worked.
If all else fails, I'm going to buy a towel rail with a heating element in it!!!
Thanks again, keep the ideas coming.

 

[PaulRB]

I still reckon it is a badly balanced system.
You have definitely tuned off all the other rads? Do the rads have TRV's fitted?
Seen a similar problem dozens of times and 99% are badly balanced systems due to dodgy pipework and long runs, the other 1% is due to a blockage causes mainly by bent or squashed pipes.
The way I would be doing this is to make sure every rad is off at the lockshield valve not TRV, including hall rad if its got 2 x Lockshields. This almost always sends water to cold rad, then you need to balance the system accordingly. Just opening them all back up will not sort the problem out.
It could be air gradually building up and blocking it up, air will always rise to the top so the thing to look for is where the pipe goes up over something then back down. imagine the pipe going over a door frame. This could happen if a new pump has been replaced, the old pump may have been powerfull enough to keep pushing the air around the system.

Ok I'll give it another go and I'll try and fit an air bleed valve of some sort as high in the pipework as possible.
Thanks again

 

[fuzzy]

dont see how it can be an air lock unless theres a leak or wrong vent inlet position, bu if you say it worked before there must be an issue with what has been altered surely?

 

[PaulRB]

dont see how it can be an air lock unless theres a leak or wrong vent inlet position, bu if you say it worked before there must be an issue with what has been altered surely?

The only change I've made is to remove a bathroom rad + replace with a towel rad. I fitted one side to the existing pipework.
The other side had to be altered to line up with the rad. So I cut the pipe + extended it by 150mm. That's all.
Can't see how that would affect the other rad. They're not directly connected and I've tried turning off the towel rad to see if it helps.
I will drain down again + fit an automatic air-vent in the horizontal run in the ceiling leading to the rad. At the same time I'm going to fit 2 full bore in-line isolating valves in the flow + return pipes, so if I have to work on the rad, at least I won't have to drain down the whole system.
Thanks for all the help, I'm sure we'll solve it in the end.

 

[PaulRB]

I was wondering if I could put 2 tees in the return pipe. Have 2 flexible hoses coming off the tees connected to a drill driven pump so that, when the rad stops working, I could encourage the circulation by helping the flow thru the rad.
I know it seems like a lot of trouble but I'm clutching at straws here!
It seems as though I just have to get the hot water started and the rad will work for 2/3 days, so a little boost in the system every 3/4 days is better than a cold rad all winter!

 

[fuzzy]

The only change I've made is to remove a bathroom rad + replace with a towel rad. I fitted one side to the existing pipework.
The other side had to be altered to line up with the rad. So I cut the pipe + extended it by 150mm. That's all.
Can't see how that would affect the other rad. They're not directly connected and I've tried turning off the towel rad to see if it helps.
I will drain down again + fit an automatic air-vent in the horizontal run in the ceiling leading to the rad. At the same time I'm going to fit 2 full bore in-line isolating valves in the flow + return pipes, so if I have to work on the rad, at least I won't have to drain down the whole system.
Thanks for all the help, I'm sure we'll solve it in the end.

is it a trv on the rad? if so it could be faulty, i always use manual valves on towel rails

 

[PaulRB]

is it a trv on the rad? if so it could be faulty, i always use manual valves on towel rails

The rad that won't work has 2 wheelhead valves on--brand new. The rads with TRVs on are all new valves.
Sure it's not the valves because I've replaced them all. New rad too.
I think its a combination of a long pipe run, having to flow up and over a partition wall.
It might still be an air-lock but it doesn't feel like it. When I drain 2/3 pints from the return pipe there is no spluttering or air in the top of the rad.
I will drain down and put an automatic air release valve in the long horizontal run anyway, just in case.
I'll also put in 2 full-bore isolating valves in the flow + return pipes at the same time, so I don't have to keep draining down the whole system.
Any advice on my idea of fitting a drill-driven pump in the return pipe, to assist with the circulation.
I get the feeling that if I can get the circulation going and the hot water thru, the rad will continue to work for 3/4 days before I'd need to help it again.
It might even work continuously once the weather turns colder and we have the heating on longer and every day.It only stops working at the moment when the water inside cools right down.
Thanks again.

 

[dontknowitall]

If there's an up and over section (partition wall) does the pipe have a bleed point there?

 

[fuzzy]

i wouldnt bother with putting a drill point on, easier to find a permanent solution

the up and over sounds the obvious problem area, do you draw water from return only? try the same with the flow.

can you redirect the flow or return? leave one connected at the same point and move one connection closer the boiler?

 

[stevetheplumber]

i would track back along the pipes to see where the hot water stops my bet is a pair of ballofixes left under floor, half off,with some build up of dirt in them but that wouldnt explain the link pipe working ????

 

[Halesowen1]

If you are having problem with possible flow to rad, the last thing you want to do is decrese it even more with iso vlaves.
Unless the pipe work is going up over something then back down (making an air trap in high point) then I doubt its air.
Still say its a blockage, either on pipework or rad/valves.

 

[fuzzy]

connect the flow closer to the boiler, leave the return, therefore create a reverse return system

 

[PaulRB]

Ok guys.
The pipe to the rad does go over a wall and is horizontal for about 2 metres. I can't see the other side of the wall but I think it probably dips down so, yes, it could be an air-lock.
It doesn't "feel" like air though because when I drain from the return pipe, there is no spluttering and no air trapped in the rad.
I will still put in an automatic air vent, just in case.
I was going to put in full-bore iso valves so the flow would not be decreased.
If it was a blockage, I don't understand how the hot water is able to get thru if I drain some water from the return pipe. Surely a blockage would stop all flow?
It does seem to be a circulation problem because draining water from the return pipe encourages the water in the flow pipe and the rad will get hot and work for 2/3 days, until the water cools.( or until air builds up in the pipe ).
I just thought putting a small pump in the return pipe might be enough to keep the system working.
Thanks

 

[fuzzy]

Ok guys.
The pipe to the rad does go over a wall and is horizontal for about 2 metres. I can't see the other side of the wall but I think it probably dips down so, yes, it could be an air-lock.
It doesn't "feel" like air though because when I drain from the return pipe, there is no spluttering and no air trapped in the rad.
I will still put in an automatic air vent, just in case.
I was going to put in full-bore iso valves so the flow would not be decreased.
If it was a blockage, I don't understand how the hot water is able to get thru if I drain some water from the return pipe. Surely a blockage would stop all flow?
It does seem to be a circulation problem because draining water from the return pipe encourages the water in the flow pipe and the rad will get hot and work for 2/3 days, until the water cools.( or until air builds up in the pipe ).
I just thought putting a small pump in the return pipe might be enough to keep the system working.
Thanks

i wouldnt bother with a pump, your far better solving the problem. you say you drag water through the return, have you also tried it with the flow?
blockage, if the blockage is in the flow of course you can get water out of the return as theres no blockage there

can you re connect the flow or return closer the boiler (not both) reverse return system

 

[jase158]

Can I just clarify what has been said,
1. radiator not working
2. heat is passing through when radiator disconnected and pipe placed instead
3. replace radiator and stops working
4. drain down from one side and radiator is working fine for a couple days then stops.
5. pipe work comes from attic across house and down.

my theory would be pipework, where is it coming from? does it connect to 22mm or 15mm pipe, is the pipework to radiator 15mm, 10mm or 8mm?

just seems like there isnt enough pressure to push water all the way through, when radiator is disconnected it is pushing it far enough, but when connected there isnt enough pressure to push it along. either that or partial blockage at joint that is blocking completely when heating is cold and when you are pushing heat through it is unblocking slightly.

the way I would go would be to find where radiator connects to rest of system and replace. or connect radiator pipework to somewhere closer.

water finds easiest route, so possibly passing straight past join and not going to your radiator.

 

[nick/matt1]

try replacing the trv. also ensure you hsve no restrictions on the return pipework, or partial blockage in the feed from the top up cistern, which can cause flow restriction

 

[PaulRB]

i wouldnt bother with a pump, your far better solving the problem. you say you drag water through the return, have you also tried it with the flow?
blockage, if the blockage is in the flow of course you can get water out of the return as theres no blockage there

can you re connect the flow or return closer the boiler (not both) reverse return system

I can't drain water from the flow pipe because the drain valve is in the return pipe.
If there is a blockage how can the hot water get thru the flow pipe when I drain from the return pipe?
When I do this, the rad works ok for 2/3 days!
Thanks

 

[fuzzy]

the water may not be coming from the flow pipe is my point, it CAN come from the return pipe

and you havnt answered my question, can you tee either the flow or return closer the boiler?

 

[PaulRB]

I think you're right. The problem is in the system before the rad but I can't get at the pipework there.
I just find it strange that I can get it working for 2/3 days before it packs up again.
As long as the water in the pipes is hot, the circulation seems to be ok.
The problem occurs as the water cools down.
I thought putting a small drill-driven pump in the return pipework might give the system the boost it needs to keep working.
I would only need to activate the pump for seconds, until the hot water comes thru again.
Thanks.

 

[PaulRB]

The hot water is definitely coming from the flow pipe because I can feel it coming down the pipe as I drain cold water from the return. It then circulates ok for as long as the heating is on. It seems that once I have the system flowing, it works ok but stops when the water cools.
Not sure if I can tee closer to the boiler.
Thanks

 

[nick/matt1]

would still look to balancing the system, and changing trv. The pipework after the rad is more likely the problem, unless as already stated there is a restriction in the feed

 

[JimField]

This is worth a try . Remove RAD close flow valve leave return open and close all other radiators.If this is a gravity system cap the vent pipe to the Fill and expansion,if a pressurised system no problem .Connect mains pressure to the heating system and open the return on the problem rad .The idea is to blow all the crap back out of the return pipe of this problemed area ,it may take some serious flow and keep pulling water off ,sounds like a bottle neck has become blocked and needs reverse flow to clear it. Hope this helps.

 

[jase158]

it seems to me that you are looking for an easy fix and imho there is no quick fix,

your options.

1. Put the pump on and AAV push the pump every few days, this will get the system running and like you say maybe when it gets hotter, you will not have to keep doing it, but if it is a blockage in the summer it will get worse. Remember to put 2 iso valves on there so it doesnt leak after you finnished and a iso valve on pipework that is being taken out so it doesn't just circulate in a circle.
2. Take floorboards/ walls up, replace joins and check for dirt
3. Get the system powerflushed and hope it is sorted by this (not sure this will work but might do)
4. Re-pipe the pipework so that it is connected to another rad

My opinion is get a proffesional in to do the work properly, get it fixed now and you wont have problems later

 

[fuzzy]

when hot it works when cold it doesnt. sound like a section is working on gravity and therefore the pump is missing the rad out as such. can you swap the tee for a swept tee

 

[jase158]

when hot it works when cold it doesnt. sound like a section is working on gravity and therefore the pump is missing the rad out as such. can you swap the tee for a swept tee

I was thinking something like that but didnt know it was possible, thanks fuzzy, learn something new every day

 

[nick/matt1]

this rad isnt run on when hot water only selected by any chance?

 

[stubob3000]

You definately need a permanent solution to this.....

There seems to be 2 major changes to the system since the rad hasnt worked (but did for 18 years?) A new towel rad and a new pump. I agree with an earlier post that the pump may not be as powerful as the older pump (so hot water is having a harder time trying to get to this lonely rad through longer than normal pipework over obstacles etc) If this is the case? Then if you tee this rads flow closer to the boiler you will be removing an awkward dead leg of pipework which may work??

But we need to also look at the other changes you have made since it stopped working... Can you remove the towel rad and place a temporary bridge between the flow and return (like you did in the cloakroom, using 15mm) Just to rule out the fact since this rad was installed with its new (but could be faulty) TRVs the cloakroom rad didnt work? worth a shot?!

The other major defect could be a possible blockage in the system (air or debris)? Again the original pump may have not had an issue....
The best fix is probably to power flush piipework to be on the safe side, although I would also recommend re-doing the flow and/or return pipework to rad?

Just a brainstorm here, but will the system all on max, including all TRVs and lockshields (and thermostats) to maximum WHERE exactly does the hot pipework stop? If you can feel around the system, along flow/return to the problem rad, where does the pipework stop being hot? If it is at a tee to the problem rad, then a swept tee (as suggested earlier) may work or the fact that this rads tail offs from the 2 pipe system are too long??

 

[nick/matt1]

could just be that the new towel rail is stealing all the heat and after a couple of hours the rad may kick in? Have you balanced the system?

 

[fuzzy]

if the towel rail replaced a previous rad its unlikely to be stealing heat as its probably a lower output

it may be more restrictive and with a less powerful pump it simply doesnt get there

 

[dontknowitall]

The way this thread's going you won't need that radiator as it will be nearly summer ...

 

[067256]

PaulRB.....you are not alone.
I have the exact same problem as you but on my kitchen rad. I thought i was all alone with this problem!!
If i shut off all other rad lockshields eventually, and i say eventually the rad warms up but does not get HOT,so frustrating.
New rad and valves fitted ( no trv on kitchen rad), tried balancing, tried pump speeds, tried bleeding the air........water coming out of all rads when bled. Have drained system and refilled again....put in inhibitor. NOTHING!!!
return pipe is hot, flow is cold!
Even the plumber i called was baffled.
1 THING THOUGH,
With all the above done, i am getting a constant noise of flowing water at the boiler and also at the pump in the airing cupboard.
Boiler fires but only for about 30 seconds
PLEASE HELP.

 

[Halesowen1]

But he has said he has turned off all other rads, so it would have nothing to do with the towel rad. As with them all off it still dont get hot.

 

[trev69]

have you taken the automatic valve apart and checked the components inside the needle sticks in that aswell ,and peronally i would put a trv and lockshield on the rad

 

[trev69]

sounds like the pump in the boiler is dying on you

 

[nick/matt1]

could be scaled up. boilwer only fires for few minutes therefore heat is lost before radiator. it seems that as the return is hot and the flow is not, the valves could be the wrong way round... and causing restriction. either that or the pressure on the return is greater than the flow so it cant push round.

 

[PaulRB]

Ok guys.
I can't believe so many people are willing to think this thru and offer advice!!
Just to be clear; all rads have new valves, some are TRVs and others wheelhead.
I have fitted a brand new pump.
I have drained down twice in 48 hours and the water coming out of the system is lovely and clean.
Before fitting the new rad I fixed a hose from the o/side tap ( off the mains ) to both valves + blasted thru to try and clear air or blockages.
The pipework to + from the rad is in the 1st floor void between ceiling + floor.
It is a long horizontal run I'm sure + it could be an air lock. It doesn't "feel" like air though, because it doesn't splutter when I drain some water from the return pipe + air doesn't collect in the rad, which I would expect if it was being shifted by the hot coming thru.
It could be a blockage but I'm puzzled as to how the hot water can get thru + continue to work for 2/3 days.
I have taken a board up to reveal the pipework + turned the heating on, in the hope of feeling hot water in the flow pipe and establishing where, exactly, there may be an air lock or blockage.
However, I can only access about 4 feet of pipe, then it goes over a wall. The pipe is cold for as far as I can feel.
I'm convinced that the problem is
a) a long pipe run including having to go over the wall,
b) a tee joint that the hot water is by-passing ( but which I can't get access to without taking up carpets + floorboards + which I'm trying to avoid.
c) a lack of circulation caused by a + b

Now my plan is to drain the system and fit an automatic air vent in the horizontal pipework, hopefully solving the problem of air in the pipe.
At the same time, I was going to fit 2 full-bore iso valves in the vertical section of both flow + return pipes so I can later fit a towel rad with a heating element in, without having to drain the whole system and losing all the inhibitor.
I also thought it might be a cheap alternative to fit 2 tees in the vertical return pipe, connect a drill-driven pump between them and use it every 2/3 days to assist the circulation in the system.
I know that seems extreme but it might be enough to get us thru winter and the rad may work more continuously when the weather turns cold and we have the heating on longer.

Thanks again everyone and the more I discuss this, the more common this fault seems to be. It's nice to know we're not alone!

 

[PlumbBobBob]

is there a rad on the other side of the wall you could tee into doing away with the up and over pipe

 

[fuzzy]

im confused by what you mean 'return pipe'. i thought you said you dragged water through the flow pipe, which is it?

if its an air lock you need to drag water through the flow and then the return, they are both seperate pipes. this is how you get rid of an air lock, no need to auto air vent mate

it is either an air lock - if so fix as i advise
pump underpower - new pump
bi passing - new tee as i suggest or re pipe closer boiler for reverse return to 'even' pressures

 

[PaulRB]

im confused by what you mean 'return pipe'. i thought you said you dragged water through the flow pipe, which is it?

if its an air lock you need to drag water through the flow and then the return, they are both seperate pipes. this is how you get rid of an air lock, no need to auto air vent mate

it is either an air lock - if so fix as i advise
pump underpower - new pump
bi passing - new tee as i suggest or re pipe closer boiler for reverse return to 'even' pressures

ok rad has 2 pipes - 1 bringing hot water, other returning water to boiler. I think of them as the flow and return pipes.
There is a drain valve on the return pipe which I can use to drain about 2/3 pints.
This is replaced by hot water thru the flow pipe and, once I have some circulation, the rad will work for 2/3 days, until the water in the system cools. Then I have to drain again. ( obviously I can't keep draining so I'm looking into why the rad works for 2/3 days then stops )
I think you're right about the hot water by-passing the flow pipe but I can't get at the joint to put in a swept tee.
Not the pump - it's new + working fine.
Thanks

 

[nick/matt1]

reduce the flow toradiator which comes off the tee to allow flow through this rad

 

[Halesowen1]

YOU NEED TO GET A PLUMBER/HEATING ENGINEER OUT NOW AS THIS IS WORTHLESS.
Its down to something you have done whether you believe that or not. This cannot just happen for nothing, Fitting air vent wont do nothing, fitting tees and a drill pump is pointless.
It needs draining, putting drain off on this problem rad pipework, fit higher powered pump, fill back up, then turn every other rad off completely, if no heat still leave running and start draining from rad with hose, this will draw water around.

 

[dontknowitall]

I'm beginning to wonder if the flow and return to/from the radiator have both been plumbed into the flow (or return) on the heating circuit.

 

[Halesowen1]

Plus this tee wont do anything, if no water will get round with others all off it aint gonna do anything.
If it all worked OK before then the system needs getting back to how it was.
You do not know if pump is working OK, just because its new means nowt.
Get a more powerfull pump. If you cannot draw heat to this rad with others off its circulation problem, be that air (no), This tee you have been told (no as it was fine before), Maybe faulty rad or pump causing obstruction of flow or not enough power to feed rad.

 

[Halesowen1]

When you have eventually been getting heat from this rad after removing and putting a link between, have you then gone to all other rads and just opened them up??
As I feel it is pump and when you open them back up again it is just easier for the water to flow around these other rads that are piped closer. balance the system correctly after getting heat to it.

 

[fuzzy]

ok rad has 2 pipes - 1 bringing hot water, other returning water to boiler. I think of them as the flow and return pipes.
There is a drain valve on the return pipe which I can use to drain about 2/3 pints.
This is replaced by hot water thru the flow pipe and, once I have some circulation, the rad will work for 2/3 days, until the water in the system cools. Then I have to drain again. ( obviously I can't keep draining so I'm looking into why the rad works for 2/3 days then stops )
I think you're right about the hot water by-passing the flow pipe but I can't get at the joint to put in a swept tee.
Not the pump - it's new + working fine.
Thanks

you could be drawing air from the flow yes, and this may heat up the rad yes, but if theres an aitr lock on the return it wont work or will partially work. shut the flow valve and draw the water through, that will drag water from the return pipe

is the pump the same size and power? what setting is it on?

 

[PaulRB]

Reply to Halesowen 1

Ok Ok I hear you!
Trouble is, I phoned around to get a plumber in.
Regular guy said he was just too busy, 3 others didn't even get back to me.
I've spoken to about a dozen plumbers down at the local plumbers merchants and they've all said the same thing ie; air lock, sludge, long pipe run, by-passing tee etc.
When I tell them what I've done they all scratch their heads and say they would've done the same.
If I could find 1 plumber who said " I know what that is. I've come across it before. Do this." I'd jump at it.
The only thing I want to avoid is taking up the carpet/floorboards in the other room to access the pipe joint.
However, that may be the only way.

Can you tell me why I can get hot water into the rad AND it will carry on working fine for 2/3 days before stopping.
If the new pump can circulate the water ok for 2/3 days why do you think its the pump?
Appreciate your help, thanks.

 

[fuzzy]

well its certainly something causing it, im still not convinced you have all the air out of it, until you isolate the return and draw it from the flow pipe then do the same with the flow you will never be sure all the air is out

air can be trapped at the top of pipes but not the full bore, therefore restricting flow but not stopping it. if thi sis a long run when it fires from cold it may bi pass. you have to keep trying these things or you may never find out

once you have eliminated this check the pump power, the speed you have it on.

then if all this is fine and you say valves are fine and pipework fine you only have option of putting swept tee in and/or re pipe if you want a proper solution

 

[PaulRB]

Thanks.
When I drain down the system to fit an air vent and iso valves I suppose I could also fit a drain valve in the flow pipe and try shutting off the return valve + drawing water thru the flow pipe.
I've tried running the pump on all 3 settings but no joy.
I really think it needs a swept tee but I didn't want the hassle of gaining access.
Might have to swallow it and take up the carpet.

Thanks again

 

[Halesowen1]

Why are you fitting iso valves and air vent??
All the system worked fine before with nonw of this. This will not solve your problem.
Have you balanced the system correctly once you have had heat to the rad??
Did you buy the identical pump??
Why would it need a swept tee?? it has never had one before.
Think logically, none of these things on system when it was working fine so why would you put one in now??
Where abouts are you?

 

[jase158]

are the pipes level, bit of a long shot but if they have air in a bit of pipe which isnt straight, the air will stay there, with using for a few days steam (or something similar as wont be steam as has to be 100 degrees to get steam) could buid up and cause it to completely block, when draining slightly it is removing a little bit of air and then building up over a few days?

told you it was a long shot, but to find out if this is even remotely possible, check the pipes in loft to see if they are level. if not, try to lower them.

 

[fuzzy]

have you altered the height of the peipes when you swapped the rad? that may have put a air lock situation in the pipes?

dont worry about aav's just draw the water from each pipe seperately, that will clear the air if there is any

if its dragging air in it will be poor vent inlet position or a leak on the negative side of the system

 

[PaulRB]

Ok.
Fitting air vent in pipe in case it is an air lock.
To do this, I will have to drain the system so I might as well fit iso valves in 2 pipes feeding the rad so that, at a later date, if I can't solve the problem, I can fit a towel rad with heating element without having to drain the whole system.

Yes I bought the identical pump.
I'm in Dorset and around here plumbers are like gold-dust. It does P me off though, when they don't even return a call.
Haven't altered height of pipes. Already thought of that and I took up floorboard in wardrobe to access pipework in the hope that I could lower the pipework and reduce chance of air lock.
Not possible because pipes travel over 2 walls.
I will try dragging hot water into rad with all others turned off and leave the system like that for 3/4 days to seee if rad continues to work.
If it does, that would point to balancing of system.
If it stops working after 3/4 days I don't know what could be the cause.
I suppose I find it so frustrating because it does work properly for those 2/3 days.
Thanks

 

[JimField]

If all else fails pressurise it, with a Expansion vessel , filling loop and Prv valve you can buy them as a kit. Not too expensive that would be my next move,bit of a strange one, .Good to hear all the idea's though.

 

[fuzzy]

Ok.
Fitting air vent in pipe in case it is an air lock.
To do this, I will have to drain the system so I might as well fit iso valves in 2 pipes feeding the rad so that, at a later date, if I can't solve the problem, I can fit a towel rad with heating element without having to drain the whole system.

Yes I bought the identical pump.
I'm in Dorset and around here plumbers are like gold-dust. It does P me off though, when they don't even return a call.
Haven't altered height of pipes. Already thought of that and I took up floorboard in wardrobe to access pipework in the hope that I could lower the pipework and reduce chance of air lock.
Not possible because pipes travel over 2 walls.
I will try dragging hot water into rad with all others turned off and leave the system like that for 3/4 days to seee if rad continues to work.
If it does, that would point to balancing of system.
If it stops working after 3/4 days I don't know what could be the cause.
I suppose I find it so frustrating because it does work properly for those 2/3 days.
Thanks

may work for 3/4 days if a partial air lock, thats why i asked if the pipes had moved, ive had it before, long shot i know but we are running out of options. dont put aav iin, its a waste of time, drawing water out of each pipe will solve air problem if it is. shut of both valevs and take off rad, connect hose to each outlet and drag through

 

[PaulRB]

Thanks Fuzzy.
Haven't moved any pipes.
I'll have to fit a drain valve on the flow pipe in order to drag water thru.
Already have one on the return pipe.
Are you saying that, once I draw water thru both pipes, any air should be gone and the system should work as normal?
What worries me is that after working for 3/4 days air may be getting back into the system, or do you think I'm not actually purging the system of air and its the same air gradually returning to the pipe, causing a blockage?
Wouldn't an air vent cover that possibility?
When you talk about a poor vent inlet position, do you mean the pipe that hooks over the expansion tank in the roof?
If so, couldn't I extend that pipe to end underwater, so it couldn't suck in any air?
Thanks

 

[fuzzy]

i cannot ensure you that it will fix the problem but it will eliminate the problem being air.

fitting a aav could cause issues, if air is entering the system theres a problem, if you try to fix this by aav you will keep bringing in fresh water which is untreated and has fresh oxygen, therefore it will cause corrosion, not a good idea. aavs are only there to help initial filling

dont extend the pipe, it shouldnt suck in air, were is the vent (hooked pipe) inlet, cold feed to sysem and pump in conjunction with each other?

 

[PaulRB]

There is a vent pipe hooked over the expansion tank in the attic.
Directly below the expansion tank is the airing cupboard with a copper hot water tank, pump and 3-way valve.
The boiler is in the garage.
I think I need to shut the wheelhead valve on the flow side and then drain some water from the system, clearing it of air in the return pipe.
Then shut the lockshield valve on the return side and drain some water from the system, clearing it of air in the flow pipe.
Then I shouldn't have any air in those pipes.
You may be right that air is trapped in the return pipe which is stopping the circulation, and I thought it was in the flow pipe.
Thanks.

 

[067256]

Hey PaulRB....let me know how it goes. I am trailing you trying to work this out.
I eventually got my rad to warm up by turning all other rads off but it took a loonnnngggg time and it didnt even get hot....just warm to the touch!!
Put the rads back on and kitchen rad still does not work.

 

[fuzzy]

whats the output of the new rad compared to the old rad?

im guessing that restriction in a towel rad is greater than normal rad which may restrict flow more than previous and contribute to it not/struggling to circulate

 

[PaulRB]

Thing is, I've shut off all the other rads and I've shut off just the towel rad and it still hasn't helped.
The new rad is a direct replacement for the old one.
I know from talking to people that this is a very common problem. A rad stops working for no apparent reason, usually when you switch on the heating for the first tine after summer.
Thanks

 

[Phil]

Can't really suggest anything that hasn't already been said other than fitting auto air vent is a bad idea. Yes if it is air it will work but when you move house it will be still there under the floor unseen and may cause a plumber agro!

Like the diy'er who tiled his bathroom floor over his c/h pump and a year later it needed replacing.

Nothing worse than working on a system thats been 'messed with'.

Get those carpets up Paul!

 

[fuzzy]

have you drawn the water through each pipe yet?

 

[PaulRB]

Sorry, haven't had time yet. Still gotta work!
I hope to have a go on Thursday.
Realise I don't need to put a draincock on the flow pipe, I'll just turn off the valve at the rad. That way I know when I drain some water from the return pipe it must be replaced with water from the return pipe, and hopefully will flush out any air in the pipe.
I'll let you know how I get on.
Thanks

 

[fuzzy]

some drain off valve combinations require the return valve to be open, it may be difficult for you to ensure flow from the flow pipe if this were to be the case

 

[PaulRB]

Ok, but I plan to shut off the flow valve while I drain water from the system.
With that valve closed I know the water coming out must be from the return pipe ( can't come from the rad because there will be nothing to take its place ).
I hope that will force any air out of the return pipe ahead of the water.
If it works I will then re-open the flow valve knowing there must be no air in the pipes.
Then I'll see if the circulation returns to the rad.
I'm really hoping that, when I open the draincock, I will hear spluttering and know air is coming out!!
If I can clear all air out of these 2 pipes there should be no reason for the water not to circulate.
If it still doesn't work at least I know it can't be an air lock.
Gonna try this tomorrow.
Thanks again.

 

[fuzzy]

Ok, but I plan to shut off the flow valve while I drain water from the system.
With that valve closed I know the water coming out must be from the return pipe ( can't come from the rad because there will be nothing to take its place ).
I hope that will force any air out of the return pipe ahead of the water.
If it works I will then re-open the flow valve knowing there must be no air in the pipes.
Then I'll see if the circulation returns to the rad.
I'm really hoping that, when I open the draincock, I will hear spluttering and know air is coming out!!
If I can clear all air out of these 2 pipes there should be no reason for the water not to circulate.
If it still doesn't work at least I know it can't be an air lock.
Gonna try this tomorrow.
Thanks again.

mmmm, id be more confident if you did the same with the flow, your only pulling water from return, you really should do the same with the flow to ensure 100% you have no air

 

[PaulRB]

Yeah, I will.
Thanks

 

[fuzzy]

let us know how it goes

remember you must do the same with both pipes to ensure there is no air in them. doing it with one valeve closed only ensure that pipe has not air in it

if you only do it with the return as you suggest it only ensure the air is out of that one, doesnt prove anything with the flow

after tyhis it may not be air but at least you can eliminate it once and for all

 

[PaulRB]

Ok Guys, ( especially Fuzzy ), this is what I've done today, Saturday.
Tied up the ball-cock in the expansion tank so it doesn't fill with new untreated water.
Turned off both valves on problem rad. So any water I drain must come from return(-) pipe and not from rad or flow(+) pipe.
Opened draincock and drew off 1/2 bucket of water. Plenty of spluttering and flow stopped for 1/4 to 1/2 a second before continuing, so obviously a lot of air in return(-) pipe.Took bucket up into attic and refilled expansion tank.( level had not dropped below outlet pipe so no air being drawn into system )
Repeated process and this time water flowed as normal.( refilled expansion tank )
Opened both rad valves and drew off another 1/2 bucket in case there was air in the flow (+) pipe but water flowed nicely. ( refilled expansion tank )
Went round and turned off all other rads and put heating on.
5 mins later we had hot water coming thru pipes and rad got very hot. Turned all other rads back on and ran system for 1 hour. Everything ok.
However, I've had the rad working before so I won't know if this has solved the problem yet. I've turned the heating off and I'm gonna let it cool right down for 24 hours and then fire it up again.
Fingers crossed!!
At least I know there was air in the pipework, now I have to wait and see whether air is getting into the system, which is a different problem. I hope the air was trapped in the pipe when I refilled after replacing the pump and, now I've purged the system, it works as normal.
I'll let you know tomorrow.
Thanks guys.

 

[fuzzy]

fingers crossed, keep us posted

 

[Halesowen1]

Balance the system.

 

[PaulRB]

Ok.
So far so good.
Put the heating on this pm and hot water came thru straight away.
Still not 100% sure the problems solved. It'll take a few days of working before I can relax and put it out of my mind.
I still have to balance the system
Meanwhile I will keep you all posted as the week goes on.
If air isn't getting into the system I should be alright.
I know a lot of people have this problem and are following the thread so I think I should point out some of the main points because different systems and installations would require different solutions.
However, with all the help on hand here, I'm sure most problems can be solved.
I have a gravity fed, 2 pipe system with an expansion tank in the attic.
There is a cylinder in the airing cupboard together with a 3-port valve and pump.
The boiler is in the garage.
Downstairs our floors are concrete so all the downstairs rads are fed from above in a "loop" system.
All downstairs rads have draincocks on their pipework so that when you drain the system, you have to go round each rad and drain them individually if you want to completely drain the system.
I understand that the "loop" system is susceptible to air locks when filling up the system and that appears to be whats happened to me.
I've been lucky because I have draincocks on every rad but other people may not so the things I've tried may not work for everyone.
However, the amount of help and support provided by the guys on this forum should enable everybody to solve their problem.
I thank you all for taking the time and trouble to help out and sticking with it when nothing seemed to be working.
My wife thanks you all too!!!
Hopefully I will report that all is working fine in a weeks time.
Cheers

 

[PlumbBobBob]

fingers crossed all goes well

 

[PaulRB]

I'm crossing everything mate!!!

 

[Halesowen1]

What you have is a regular pumped Y plan system, these are very common. Your problem is not so common though, every system is full of air when it gets filled but 9/10 are vented easily. So lets hope for your sake it is not drawing in air or air catching somewhere.

 

[067256]

Ok Guys,
I have done exactly as described by Paul and still something not quite right.
My kitchen rad has a lockshield with bleed valve on return and wheel type on flow. I have shut off both valves, put bucket under bleed valve opened bleed and no water has come out!! but if i open the flow valve water starts flowing out lovely and the hot water starts coming thru the flow pipe....rad then starts warming up. Filled about half a bucket shut off flow valve and refilled the F+E tank. There were small small splutters of air so did the same thing 2-3 times more by opening the flow valve again.
Now with the flow valve off i open the lockshield fully and open the bleed valve............a trickle of water coming out!!!!
BLOCKAGE?????? As i am writing this the bleed valve is open fully and the water is still trickling out.

 

[067256]

1 more thing.
Thought i would try the rad with the heating on again.
Shut all other rads off at there lockshields, turned on the heating, boiler fired and lasted for about 60 seconds then went off. Boiler fired again a further 2-3 times then eventually cut out on the boiler overheat thermostat. Could this be due to the blockage there is a build up of heat at the blockage and circulation is affected????

 

[fuzzy]

Ok Guys,
I have done exactly as described by Paul and still something not quite right.
My kitchen rad has a lockshield with bleed valve on return and wheel type on flow. I have shut off both valves, put bucket under bleed valve opened bleed and no water has come out!! but if i open the flow valve water starts flowing out lovely and the hot water starts coming thru the flow pipe....rad then starts warming up. Filled about half a bucket shut off flow valve and refilled the F+E tank. There were small small splutters of air so did the same thing 2-3 times more by opening the flow valve again.
Now with the flow valve off i open the lockshield fully and open the bleed valve............a trickle of water coming out!!!!
BLOCKAGE?????? As i am writing this the bleed valve is open fully and the water is still trickling out.

is the pump on?

 

[fuzzy]

1 more thing.
Thought i would try the rad with the heating on again.
Shut all other rads off at there lockshields, turned on the heating, boiler fired and lasted for about 60 seconds then went off. Boiler fired again a further 2-3 times then eventually cut out on the boiler overheat thermostat. Could this be due to the blockage there is a build up of heat at the blockage and circulation is affected????

heat not getting round, is pump working? rad vales open? valves on pump open? history of sludge?

 

[067256]

pump is working,
rad valves open,
no history of sludge as far as i am aware, only been in the house 18 months.
heating on, pump running, open bleed valve on return...just a trickle of water coming out. Rad has a new valve aswell.

 

[fuzzy]

dont vent when pump is on, make sure its off or could actually suck air in

make sure vales is open, sometimes if new and dpendant on type the washer can be stuck on seating, leaves valves shut, take off rad and slowly open valves to check

 

[PlumbingBud]

Do you have microbore pipe anywhere? 10mm or less.(Sorry, but I couldnt be bothered reading 10 pages!)

 

[067256]

Pump switched off.
Closed both valves on rad and removed the rad in question. Opened flow valve and get a good flow of water.
Open lockshield valve and only a trickle, there is nothing wrong with the valve as i have actually tried it on another rad when i fitted a TRV.
I'm just convinced now that it is a blockage.

 

[PaulRB]

Rad still working!!
Fingers still crossed!!
Back again tomorrow.