Split coil am wondering?

[mutley racers]

I have been to a house where in the morning the overflow is flowing, but as soon as you flush the toilet or use tap, it stops. So, I have changed the ball valve, and i get another call 2 days later to say it is over flowing. The house is empty at the moment and I installed a shower pump in there. Now it was not doing this before apparently, so am wondering if I could have caused it if it is a split coil?

What are the things I should look out for tomorrow when i go to check? I put a pump on the hot side and the cold is from the mains. I used a pressure balancing shower valve to equal both pressures. And, it only happens during the night time.

Cheers fellers

 

[EPH]

Turn the hot isolation off on the shower pump, could the cold main be passing through the shower?

long shot I know.

 

[josh]

It would stop it when you flush toilet etc as its lowering the tank level but will overflow again. As the house is empty assuming the F+E cistern water level is higher then the CWSC water level isolate the ballvalve and turn of the hot to your pump and see if it does it again, then i would be fairly confident it was a split coil (F+E water level would drop). If it doesn't but then does again when the shower pump is back on (no check valve within shower pump?) then could possibly be the shower. We'v had that before.

 

[mutley racers]

Thanks for the reply guys. The f&e tank is lower than the cwsc. But could I have caused this by installing the shower pump? Also, the shower is not being used so surely the water will not be able to go up the hot side. Will it?

 

[Dotty]

You got iso valves on the shower pump? turn them off frst and monitor it.

 

[josh]

It cant be the coil then, it would overflow out of the F+E if the coil was split as it is lower. I should think its the cold pushing back through your pressure equalising valve, just wants a single check valve on the hot side, thats my guess.

 

[chris watkins]

(shower valve) Yes it will, & probably is. What check valves are there on the shower valve ? the point where the high pressure cold main connects to the lower pressure hot side ? I take it that the pump you installed was a positive head one i.e. only comes on when water flows through it.

 

[mutley racers]

Yes I have iso valves. So that shall be my first port of call. If the coil was split, wouldn't there be dirty water coming from the hot taps? And if I turn the heating on and it is a split coil, it should be more noticeable do you think?

 

[EPH]

You could be talking a very small hairline fracture in he coil, that would be heavily diluted in 150 litres of cylinder and whatever your cistern is, normally.

 

[mutley racers]

Sorry Chris is that yes it will and probably is a split coil? It is a positive head pump I installed and I have a check valve on the cold and iso valve on the hot just after the pump. The pump is in the loft. Oh I think I know what you mean Chris, is that the cold is going up the hot even though the shower is not being used

 

[Nostrum]

It's not the coil. Read Josh's post.

 

[chris watkins]

Sorry Chris is that yes it will and probably is a split coil? It is a positive head pump I installed and I have a check valve on the cold and iso valve on the hot just after the pump. The pump is in the loft. Oh I think I know what you mean Chris, is that the cold is going up the hot even though the shower is not being used

You got it, often happens even on un-vent systems when you think the pressure are equal but the hot increases due to expansion & the check valves that should be in place on the shower valve do not hold up. (high pressure cold pushing back up the cold feed to cause the cistern to O/F, would be my guess.

 

[mutley racers]

Right so the 1st thing I shall do tomorrow is put a check valve on the hot supply and see if that's the trick. The same as everyone else said really by turning off the hot iso valve. Thanks guys. I really appreciate it. I hope it is that and not a split coil

 

[chris watkins]

Mutley, I think the others were suggesting the isolation bit to confirm that this was the problem before you go steaming into pipe alterations (apart from anything else the shower valve should have already been fitted with single check valves in both the hot & cold inlets to stop the contamination of the water supply under the water regulations !!)

When did you say your water reg's course is booked for ??? LOL

 

[mutley racers]

Hey low blow there. You're only supposed to put a checkvalve on the cold main to stop the hot going into the main if I remember correctly. Or am I wrong? Maybe I should check in my book again. Cheers Chris. Keeping me in check you are. Check ha ha

 

[chris watkins]

Hey low blow there. You're only supposed to put a checkvalve on the cold main to stop the hot going into the main if I remember correctly. Or am I wrong? Maybe I should check in my book again. Cheers Chris. Keeping me in check you are. Check ha ha

Trying to keep you in (two) check, you know me, cos its one on the hot & one on the cold I am afraid. R15.13.2a:

 

[kay-jay]

while there installing the check valve make a note of water levels in the the f+e and cwsc. water will always find its own level so if coil was split the water level in the lower tank (f+e) would rise and rise trying to reach the water level of the higher tank.

 

[mutley racers]

Ok, I am going to study my water reg book this weekend. Brush up on a few things. Cheers Kay jay, pretty sure it's cwsc that's overflowing and it's higher than the f&e. So it can't be a split coil. Phew

 

[mutley racers]

So cool having a smartphone. I am sitting in my van at traffic lights on the way to 1st job and chatting on the forum. Maybe it's actually quite sad

 

[DirksPlumbing]

Well, unless the overflowing happens in the F+E tank we can surely exclude a split coil as mentioned countless before. Fitting a check valve on the hot side will immediately stop the problem of getting hot water out the shower as the gravity will not be able to overcome this in specific if the cold is pushing it shut anyway. I am afraid you either need a universal pump or you need to run tank fed cold to the shower (pump).
Funny you stating water regs but do not mock the fact that there is a mains and a tank fed inlet to the mixer. Which to my knowledge is only allowed on mixers that are suitable. And that excludes roughly 100% of the shower mixers.

Edit: There once was a venturi driven shower mixer which was suitable but I never found a supplier.

Edit2: the magic wording used usually is balanced pressure.

 

[mutley racers]

I have used a pressure balancing valve on the shower and so this is allowed to be run by the mains water supply. Thanks for the info Dirk. It's much appreciated

 

[DirksPlumbing]

I have used a pressure balancing valve on the shower and so this is allowed to be run by the mains water supply. Thanks for the info Dirk. It's much appreciated

Should use my glasses, sorry.

 

[mutley racers]

So is this shower valve ok do you think Dirk? A checkvalve on the hot won't or will do the job? Don't apologise, I like as much advice as I can get. At least if it doesn't concern this job, it will be in my mind for others

 

[chris watkins]

Just so I am clear in my own mind the set up you have is a mains cold & a gravity hot which runs through a single impeller positive head pump to boost the pressure & flow rate, both the hot & the cold then go on through an RWC water pressure balancing valve before going onto a shower mixer valve, is this correct ? if so what is the main pressure & the pump rating ?

 

[mutley racers]

The set up is all correct what you say but I have put a pressure balancing shower valve on with the cold mains with a adjustable pressure reducing valve taking it to 1.6 bar, the same as rating as the single impeller hot pump.

 

[DirksPlumbing]

So is this shower valve ok do you think Dirk? A checkvalve on the hot won't or will do the job? Don't apologise, I like as much advice as I can get. At least if it doesn't concern this job, it will be in my mind for others

A check valve on the hot usually prevents the shower pump from operation if it is not a universal head one. Had many crossflowing shower mixers before, causing all sorts of nonsense.

I am not sure what pressure balancing valve you have used and as well what sort of pressures you have on your site. I found some manufacturers only specifying 8bar maximum which we can get close to in some places here at peak times. And I take you have fitted it the right way round (don't think of this being a stupid question, happens to the best too, they just keep it silent). It could point out a malfunction of the valve as well (dirt?).

 

[DirksPlumbing]

The set up is all correct what you say but I have put a pressure balancing shower valve on with the cold mains with a adjustable pressure reducing valve taking it to 1.6 bar, the same as rating as the single impeller hot pump.

Seems doubled up having a PLV and a balancing valve? You could reduce the CWM pressure easily to 1 bar without loosing function as the 1.6 is peak.
Might help it but generally if it is crossflowing it indicates a problem anyway.

 

[mutley racers]

The pressure valve is the right way around and I have put them on the wrong way on occasions. So why does the check valve stop the pump operating? Is that if you put it either side of it? As I know they say not to put one before the pump

 

[DirksPlumbing]

The pressure valve is the right way around and I have put them on the wrong way on occasions. So why does the check valve stop the pump operating? Is that if you put it either side of it? As I know they say not to put one before the pump

One before the pump could cause pressure rise till the pump bursts. Especially in your situation. Positive head pumps have flow sensors. But the check valve does not allow flow to establish as the spring will keep it (near) closed.
For the pump it seems there is no demand and therefore no action.
You sometimes get that to work but often not for long. Once things get a bit stiff by latest it is stopping function.

Universal (negative head) pumps have pressure switches and hold a pressure sufficient to open the check valve. And the other thing they hold is the price tag.

 

[mutley racers]

I have just looked on the salamander site and they have checkvalves fitted on the hot supply from the pump? So it must be ok?

 

[josh]

You mention that the pump is in the loft and if you did put a check valve on the hot up there i don't think there would be sufficient head to make it work, i was always told that a standard impeller pump should be fitted in the airing cupboard (or atleast a floor below the cwsc) to allow there to be enough head for it to make it work.
How come you didn't just drill a cold feed from the cwsc and had a standard twin impeller pump, those pressure equalising valves arn't that cheap are they?

 

[mutley racers]

Well that's it, checkvalve in. And pump running fine. Just need to wait until the morning now for the builder to tell me if it's stopped the overflow or not. To be honest, I don't think it matters where the pump is as long as the shower rose is below it. And mine is a metre below the shower pump and the shower pump is about 100mm below cwsc. To be honest, I was just being lazy rewards to the cold take off from cwsc. I wanted there to be mains in basin for drinking water and thought I will just use that for the shower. The ppressure reducing valve was £20

 

[chris watkins]

You are right mutley pump should work in that position but the reason it is not advisable to have the pump above the shower head, is that it is likely to allow the build up / trapping of air which can damage the pump (cavitation).

 

[DirksPlumbing]

I have just looked on the salamander site and they have checkvalves fitted on the hot supply from the pump? So it must be ok?

Well if you consider "purpose made" and "specified" then yes. It even can help to reduce the mentioned cavitation.

Just I found them (not manufacturers designed ones) getting stuck after a while. Especially if it gets slammed shut by mains pressure.

So you spend quite a bit of money and effort to design a system which has many reasons to fail.

 

[mutley racers]

Well I was out on the driving range this morning hitting a few balls and the builder calls me...well the good news is, it's not coming out of the overflow any more. The bad news is, it's coming out the light fitting above shower. He he. So had to give my balls to someone else and tighten up nut on the service valve.

Thanks for all the help guys. You're all invaluable in my progression as a plumber!!!

I see what you mean by the checkvalve Dirk. When I 1st blew into it it would not budge. Had to give it a good push with my finger. Why did they advise this if this happens to be a problem?