Overflowing Boiler – Help Please

[johnthenu]

I am a bit Naive on this, and would appreciate any suggestion/ help on the below matter.

There is an overflow of water which goes out from the boiler.

When I turn the water supply on, in about 10 min the overflow starts, hence thinking the top water tank is full I switched of the water supply, then the overflow stops as expecetd.

Then when I try to open cold water from the tap, there is no cold water…..but i get hot water…which means top tank has no water…..

I am a bit confused as to how there can be overflow without the top tank being full? Where is the over flow from?

What could be the possible reason, ballvalve , thermostat?

 

[TicklyT]

Do you have any mixer taps?

It sounds like the sort of thing that happens when mains pressure cold water and gravity hot supplies are connected to a mixer tap or shower valve etc where there is direct communication between the hot and cold inlets.

Higher pressure cold water forces the hot water back into the cylinder and storage tank, and eventually out of the overflow. The only way to stop it is to shut off the cold supply at the stopcock.

A non-return valve on the hot inlet of the offending mixer is often the solution to the problem.

 

[johnthenu]

No i Dont have any Mixer taps....

These are the things i have noticed:
1, As soon as i stop the cold water supply to the main tank, there is not cold water on the taps in the house.
2, If i leave the cold water supply on, then the overflow starts within minutes.

So its like a catch 22, no cold water in the house if the cold water supplys are off, or overflow when the cold watter supply is on.

So i have to manualy open the cold water supply every time i need cold water.....

 

[mysteryman]

Or ... do you have a Fortic cylinder - one with a copper cold tank on top of the hot water cyl?

If so, an old trick of some plumbers was to fit the overflow very high up, higher than the ball tap and expansion pipe. If the ball tap lets by, the water level rises, and water flows DOWN the expansion pipe into the cylinder. It eventually rises to exit the overflow. Meanwhile, the hot water in the cyl thermo-syphons up into the cold tank, heating it up.

If you then turn off the water main, and open a cold tap, hot water can flow back through the ball tap into the cold pipes and out through the cold tap.

Unlikely, but not impossible!

 

[electronicsuk]

I think you're getting yourself very confused here. And if you're not, I certainly am.

When I turn the water supply on, in about 10 min the overflow starts, hence thinking the top water tank is full I switched of the water supply, then the overflow stops as expecetd.

Then when I try to open cold water from the tap, there is no cold water…..but i get hot water…which means top tank has no water…..

If you've turned the water supply off, by which I assume you mean at your main stop cock, why would you expect cold water at all your taps? Likewise, there will be hot water, as it's fed from the CWS tank. Why you think this must mean the top tank is empty is beyond me.

It just sounds like a leaking filler valve on the CWS tank to me. If it only takes 10 minutes to overflow then go up into the loft and see if you can observe the filler valve dripping well after the tank has refilled.

 

[daneski88]

Precisely - ball valve in the CWS is passing, or the ball has developed a puncture. Simple as that.

Cold water taps are mains fed, so will have nothing to do with CWS tank in the loft.

 

[vulcancontinental]

does the boiler fire when you open a hot tap when it's working normally?

If you've an overflow from your boiler it may be a combi boiler. If you have left the filling loop connected and open it may be filling the system slowly until the pressure relief valve opens. If you open the cold tap it may be pulling hot water from the boiler into the cold main and hence to the tap.

I may be completely wrong and have the wrong end of the stick; it wouldn't be the first time but the description is difficult to understand.

 

[electronicsuk]

I may be completely wrong and have the wrong end of the stick; it wouldn't be the first time but the description is difficult to understand.

I get the impression 'boiler', as far as the OP is concerned, is referring to the HW system as a whole, probably more specifically the HW cylinder. I don't think it's a combi, otherwise when the CW feed was turned off, there would be no HW either. But who knows... the terminology is all over the place!

 

[vulcancontinental]

I may be completely wrong and have the wrong end of the stick; it wouldn't be the first time but the description is difficult to understand.

I get the impression 'boiler', as far as the OP is concerned, is referring to the HW system as a whole, probably more specifically the HW cylinder. I don't think it's a combi, otherwise when the CW feed was turned off, there would be no HW either. But who knows... the terminology is all over the place!

I wondered whether the boiler expansion vesslel was pushing out hot from the cold sink tap and the OP was confusing a stopcock with a filling loop (had that once).

 

[Boilerman2]

What a Post hey!!

I've read the original a few times and it would seem like a simple ball-valve job

 

[johnthenu]

Hi Folks, thanks for all the posts. Really appreciate it.
Think I am getting confused here....

When I said I turned the water supply off I meant, the water which goes into the water tank...as in this picture

http://i35.tinypic.com/14098jo.jpg
http://i37.tinypic.com/2d168wi.jpg

I thought just like hot water is stored and supplied to the taps , cold water is also stored on the water tank and supplied to the taps, therefore if I turn the main water supply off to the water tank (if I don’t/ leave it open then there is overflow) , the water will still be fed to the taps as it is stored on the tank. Is it not correct?

 

[electronicsuk]

The CWS tank feeds and all the taps and sometimes some cold outlets, such as bath and shower mixer taps. Kitchen and basin outlets are usually fed direct from the cold mains.

From what we've seen, it sounds as if your problem really is as simple as a leaky ball valve. As an aside, why does the tank say 'do not use' on it?