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.