Supply tank overflowing and radiators come with hot water on only

[Andy123]

For about a year now the radiators have been coming on with the hot water switch only on whereby i have got round this by turning the rads of but the past few weeks the small feed and overflow tank in the loft is filling up with hot water up from the airing cuboard from the feed pipe which is really hot all the way up to the tank, its not coming from the overflow pipe bent over the top of the tank but from the feed pipe at the bottom of the tank causing it to overflow onto my conservatory roof.

The system is really old about 20 years or so.

I thought it may be coil in the cylinder is broke as this would fit both symtoms but not sure.

Any thoughts appreciated.

 

[SimonG]

Its not the cylinder. Try looking at your 2 port / 3 port valve.

 

[diamondgas]

Sorry to disagree SimonG, I believe the perp is right ... Sounds like you have a cylinder coil that has become pourus.... Most definitive way to find out is isolate the mains feed to the ball valve of the F&E header tank. If it continues to fill and overflow there's usually only one other place it can get it's water from; the domestic header!

 

[SimonG]

Sorry to disagree SimonG, I believe the perp is right ... Sounds like you have a cylinder coil that has become pourus.... Most definitive way to find out is isolate the mains feed to the ball valve of the F&E header tank. If it continues to fill and overflow there's usually only one other place it can get it's water from; the domestic header!

I disagree with the cylinder . Had a problem for a year with 2 port / 3 port valve, so rather than getting fixed properly, shut down rads. Expansion now probably blocked and expanding up cold feed.

Really need a few more details and maybe some pics or failing that a call to aa plumber to have a look.

Be interesting to see what it was 🙂 🙂

 

[diamondgas]

SimonG: sounds like your are talking about the extreme rather than the norm yeh? Possible I'd agree but would go down the route I suggest first! Isolate the F&E no heating on at the mo ...

 

[SimonG]

Not really just that the only mention of an issue is with hot water. Would have been tempted down the cylinder road if it was happening cold as well. But no reason why op can't rule that out, I just believe it's a follow on to not getting the original problem sorted.

 

[Billy Bob Bob]

call a AA plumber to take a look that will be handy he can hit the cwst with a hammer stick some jump leads on the motorised valve and tow the boiler away

 

[Andy123]

Thanks for the replies, the reason i thought it was a broken coil in the cylinder is the large hot water supply tank in the loft has a much higher head of water than the small tank and once the small tank reaches a certain level to overflow, it does not seem to increase after that. I know very little about central heating/plumbing though as i come from an engineering background. Will have to try that test cheers.

 

[diamondgas]

call a AA plumber to take a look that will be handy he can hit the cwst with a hammer stick some jump leads on the motorised valve and tow the boiler away

AA as in Alcoholics Anonymous yeh? ... lol

 

[diamondgas]

Thanks for the replies, the reason i thought it was a broken coil in the cylinder is the large hot water supply tank in the loft has a much higher head of water than the small tank and once the small tank reaches a certain level to overflow, it does not seem to increase after that. I know very little about central heating/plumbing though as i come from an engineering background. Will have to try that test cheers.

Let us know what happens Andy please 🙂

 

[Kimou]

If not coil check the Return pipes on rads to see if they get hot before Flow when HW only is selected. If they are then it's heating up through the return. Maybe incorrect installation on secondary pipework so non return valve can be fitted. Might be worth giving it a clean with a mild cleanser as sludge may be making partial blockage on the return which is getting worse causing the the return to take easier less restricted path and now after a year got worse to discharge through F E feed.

 

[SimonG]

Thanks for the replies, the reason i thought it was a broken coil in the cylinder is the large hot water supply tank in the loft has a much higher head of water than the small tank and once the small tank reaches a certain level to overflow, it does not seem to increase after that. I know very little about central heating/plumbing though as i come from an engineering background. Will have to try that test cheers.

Does it overflow cold and the heating switched off as well as when you are running the system?

 

[Andy123]

Does it overflow cold and the heating switched off as well as when you are running the system?

No only only overflows when heating is turned on. From the previous post we do have one Radiator in the back room that does work at all so i wonder if that could be back flowing?

 

[mylesy]

water is meant to expand back up the feed and expansion pipe, thats why its called a feed and expansion pipe, the pipe and tank (F&E) is the equivilent of an expansion vessell. the vent pipe is equivilent to a blow off only, even water will expand up it. sometimes the overflow is set to the hieght in the tank when the water is cold rather then when it is heated, which can be 4% extra. however there is a problem with the heating being on when not supposed to be which most probably down to the electrics or controls which have eletrics in them.

 

[mylesy]

id also recommend a power flush on a system that old, could well be blockages, poor circulation, etc.

 

[diamondgas]

Hi Andy123, cupl more questions if I may.
1) with everything turned off, approximately how far below the overflow pipe is the water level in your expansion tank?
2)Again with the boiler off/on minimum, when the hot water is turned on does the water level in the expansion tank start to immediately rise?

Answers to these could dispel porous cylinder coil and indicate system design, pipework configuration issues ...

Trying to establish if you have

 

[Andy123]

Hi Andy123, cupl more questions if I may.
1) with everything turned off, approximately how far below the overflow pipe is the water level in your expansion tank?
2)Again with the boiler off/on minimum, when the hot water is turned on does the water level in the expansion tank start to immediately rise?

Answers to these could dispel porous cylinder coil and indicate system design, pipework configuration issues ...

Trying to establish if you have

1. I did not know the level before these problems but i pull out the expansion tank about 2/3 of a bucket of water before the ball cock valve kicks in, i would say about 5 inches below the overflow pipe to outside pipe.
2. Not long after the boiler starts it quickly fill up say in half an hour then does not rise anymore as its just a dribble out the overflow pipe to outside. With the boiler of it does not rise at all but stays about 5 inches below the overflow pipe.
The problem is only when the boiler is on.

Other problem is rads come on with hot water and one non working radiator in the back room which happened before the overflow problem.

 

[diamondgas]

Well that sounds like you're pump is doing the filling of the hedder Andy. Do you know if your system is fully pumped or gravity water pumped heating? I'm guessing fully pumped....

 

[Kimou]

Airlock. Decommission-say a prayer-recommission.

 

[Andy123]

Well that sounds like you're pump is doing the filling of the hedder Andy. Do you know if your system is fully pumped or gravity water pumped heating? I'm guessing fully pumped....

Not sure, i have tried turning the pump down to lowest setting which makes no difference.

The set up with the pump is an letter H in the airing cuboard, the pump is on the lower right of the H, the feed pipe to the F/E tank is the upper right where the tank is filling up from with hot water and the upper left is the overflow pipe to the top of the F/E tank which is only hot about half way up and is not overflowing into the tank.

 

[diamondgas]

Is the pump flowing towards the feed pipe? Has to be really I'd say otherwise it'd be putting negative pressure not positive on the feed pipe.... Could you post up a picture for us Andy?

 

[mylesy]

yeh it should be in the neutral zone

 

[SimonG]

Is this where I refer you back to post #2. 🙂 lol

Definitely seems to be control problem. Original fault was possibly related to 2 port / 3 port valve, depending on wether its s plan or y plan. As Mylesy a said probably some muck in there that is only going to get worse as you are now bringing in freshwater into your heating system do to the water out the overflow when hot and refill through ball valve when cold.

Open up your closed down rads and see how the overflow problem goes, if it stops with the rads on then I would get somebody to look at the controls side and you should be sorted. If not then may need a good clean, controls sorted and away you go.

Whatever you do I would do it sooner rather than later due to the fresh water you are dragging into the system.

Let us know how you get on and good luck.

 

[diamondgas]

Is this where I refer you back to post #2. 🙂 lol

Let us know how you get on and good luck.

Bowing to your superior judgement SimonG :smartass2: .... lol

I'd think more pipework configuration rather than mechanical issues though yeh? Also air in the system makes a big difference to the amount of water that can be displaced up the feed by the pump. As you mentioned in earlier posts, the more that comes to light the better the diagnosis!

Good shout and sound advice regards getting it sorted sooner rather than later!!!

 

[SimonG]

Bowing to your superior judgement SimonG :smartass2: .... lol

I'd think more pipework configuration rather than mechanical issues though yeh? Also air in the system makes a big difference to the amount of water that can be displaced up the feed by the pump. As you mentioned in earlier posts, the more that comes to light the better the diagnosis!

Good shout and sound advice regards getting it sorted sooner rather than later!!!

No bowing allowed, just lucky, didn't even consider the cylinder coil when I posted. I suppose its just down to what you see most of which'll send you down that road first when you come across it the next time. Always difficult on line with few details.

I wouldn't have suspected pipework configuration as its 20 years old, although somethings off if the rads are off and it starts pumping over.

On the sooner rather than later bit I saw an oil boiler only six years young, pulled out the burner and couldn't get it back in the hole quick enough to stop meself getting wet. Been pumping over since the day it was installed, cold water corrosion finally killed it. Seen radiators go a damn sight quicker!