Overflowing from Cold Water Storage Tank

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You can verify this by putting a 22mm gate valve on the hot water pipe after it leaves the cylinder (make sure it is AFTER the vent). Switch gate valve to off and see if this solves problem.

There is a service valve attached on the inlet pipe to the shower pump. This is on the hot water pipe you refer to and I have shut this but the overflow continues.
 
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G

Goldspoon

That only rules out the shower... no other mixers in the house.
 
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That only rules out the shower... no other mixers in the house.

There is a basin mixer in the bathroom and a sink mixer in the kitchen. I thought this hot water service pipe supplies all hot outlets in the house.
 
G

Goldspoon

Water leaves cylinder.
Water goes past iso valve (which can be switched off for testing).
Water travels via pipe to shower pump.
Water travels to basin mixer and sink mixer.

Then shower pump is also pumping basin and sink and I'm lost for now.


Water leaves cylinder.
Water then branches off to basin mixer and sink mixer.
Water then goes past iso valve (which can be switched off for testing).
Water then travels via pipe to shower pump.

Then it can be the basin/sink mixer causing problem.
 
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I think I've cracked it!

As you know I have mains cold water into my bathroom and there is an isolating valve. I have operated this valve and check the cold water tank in the loft. To my joy the hot water backfeeding into the outlet pipe had stopped. I only have to mixer valves in the bathroom and after isolating the basin mixer the problem still continued. Therefore I can only deduce that the problem lies with the shower mixer allowing cold mains to bypass the mixer and push the hot water back.

2 Solutions; 1)The solution I have come up with, is to fit a pressure equalizing valve to the pipes running up to the shower mixer.

2) Reduce the cold water pressure at the service valve feeding the mixer to half.

What do you think guys?
 
G

Goldspoon

Try turning down the iso valve on the cold - won't harm to try. You could also then try a pressure reducing valve on the cold.
 
G

Goldspoon

Ideally you should have the cold to the shower coming from the CWSC and not the mains. This is why you have a problem.
 
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Ideally you should have the cold to the shower coming from the CWSC and not the mains. This is why you have a problem.

Would it not be better to fit a pressure equalizing valve on both feeds instead of a pressure reducing valve on the cold feed.

It is indeed a strange set up for the mains cold water to be also running to the bathroom but something I'm discovering is not so uncommon accross the land. If I'm not mistaken, atleast I can drink cold water from my bathroom taps.
 
G

Goldspoon

[

Would it not be better to fit a pressure equalizing valve on both feeds instead of a pressure reducing valve on the cold feed.

I have not fitted one before to be honest. Maybe somebody else here has.
 
G

Goldspoon

It is indeed a strange set up for the mains cold water to be also running to the bathroom but something I'm discovering is not so uncommon accross the land. If I'm not mistaken, atleast I can drink cold water from my bathroom taps.

It is not strange for mains cold to be running to a bathroom. It is strange for a plumber to fit a mixer shower (or any mixing device) and take the feeds from unequal supplies.
 
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In order to fit a Pressure Equalising Valve it states, that the water heating system must be able to deliver hot water at a constant temperature, regardless of demand from the system.

I have an indirect gravity fed hot water system with a Baxi Bermuda 552 Back Boiler. Does this satisfy this criteria and sorrry for being so ignorant in this respect.
 
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A final update.

Thank you for all your help and advice. I have stopped the overflow from the CWSC. The PEV has done the trick and I have a dry patio once more.

You're all top bananas.
 

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