Continued problem with overflow

[harris48]

I still have a problem with water overflowing from my cold water storage tank.

I first thought it was the coil in the cylinder (but I have replaced this and the problem is still there). I have noticed that water overflows from the storage tank, but when i turn off the cold feed to the cylinder from the tank, water comes over
the vent pipe into the cold water storage tank. If i turn the gate valve on and off it stops and starts the water poruing out of the vent pipe.

Also when i have gate valve on the cold feed to the cylinder turned off the water pours over the vent pipe, but if i turn the mains water off the water stops coming over the vent pipe. I am at a complete loss of what the problem is - i have noticed that the cylinder does not have a cylinder stat. Please can anyone give me some advice on my next possible move.

 

[darrel]

This may sound a bit stupid but have you checked the ball valve on your cold water storage tank? is it shutting the water off when at full capacity?

 

[felix]

The answer is obvious. You have mains pressure water entering your tank-fed pipework. This is why it comes out of the vent pipe when it can't get up the cold feed. Yes, I did say up! I can understand why you thought it had anything to do with the heating coil. The pump could have been forcing water out into the cylinder but a simple test would have saved you the cost of a coil. Switch the pump off! Alternatively, if the boiler's header tank is higher then the cold tank this could push water out into the cylinder and up the vent - but then the header tank would be constantly filling up.

The fact that the vent pipe stops gushing when you turn off the mains water (rather than the pump) is pretty conclusive. The problem is to find the point of entry and the answer has to be some kind of mixer tap. Now these normally get their cold water from the tank, not the mains. The exception is a kitchen tap but if you look closely at one of these you'll see it has two distinct exit holes; the two supplies mix OUTSIDE the tap. Take a close look at anything that uses both hot and cold water and you'll eventually find something stupid.

 

[bathjobby]

Nice one felix, was pondering on this and it was starting to hurt my head. Do we know what changed that started this happening ?

 

[doitall]

To add to what felix has said.

Shower valves, mixer taps and washing machine can all cause the problem which is why single check valves shoulod be fitted.

check all fittings with a mains cold supply.

 

[kevplumb]

change the cylinder again might be the prob

 

[harris48]

Many thanks for your help everyone (my headache is starting to disappear as well) - i will check these things and let you know the out come

 

[traineegasman]

Hello to all on this site,been reading it for months,think it`s excellent.
Anyways,I have a question to all you corgi chaps out there, hope you can help me out. I am currently studying for my gas qualifications and will be qualified (acs & elements) hopefully in April.
The thing is,we have all heard
that after April no gas fitters are allowed to do any electrical hardwiring
unless you have a recognised electrical qualification. Now some people
have said it`s a one day course (How much can you learn in a day??)
others reckon you have to have 16th edition, which i believe takes years!!
Very confused and terrified! Anyone help??

 

[harris48]

I have checked the house and there are 4 points where the cold water could mix with the domestic hot water. I have placed a check valve on pipe that feeds the hot for the sink and wshing machine and also been able to isolate the hot water for the mixer tap on the bathroom basin. The problem still continues and my last port of call is the mixer shower - the hot and cold pipes for this are hidden in the wall so diffcult to put check valves on these. Would it cause any problems if i put a check valve on the cold feed to the cylinder from the cold water storage tank and also on the hot pipe from the cylinder (below the tee for the vent). If not any other suggestions please.