Hot water overflowing from cold water tank


19 Oct 2007
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United Kingdom
I have had a shower fitted, the hot water feed comes off the same pipe that feeds the bath tap, the cold is from the mains. Since having the shower fitted the cold water tank in the loft is overflowing (through the overflow pipe) but with hot water which I think is coming from the vent pipe. The shower itself works perfectly. Sorry, not sure of the make or model shower but it may be Kube. Any ideas what the problem may be?
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As your shower mixer is supplied with mains-pressure cold and tank-pressure hot (this is not very good practice)

then the shower mixer probably has an internal leak whereby the cold water is passing through the shower, along the hot pipes and pushing the hot water out.
If the mixer is fitted with service valves, turn them off and see if the problem stops.

If you feel the hot pipes immediately after using the shower you may be able to feel them going cold as the cold water pushes up them.

How difficult would it be to get a cold feed from the tank to the shower?
Every shower valve manufacturer will advocate, or stipulate, balanced supplies, whereas yours are unbalanced.

The standard questions for your fault are:

1. Which cistern is overflowing?
2. Which cistern is higher than the other?
3. What happens if you shut off the cold mains to the shower - does the cistern stop overflowing?
Who fitted this shower? Could be that you have mixed mains and tank fed hot water (BAD IDEA) or that your cylinder coil has a pin hole... is the water coming from the HOT tap normal colour or does it look a bit off colour and smell a bit?
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The OP doesn't seem very interested in the answer to his question.
Many thanks for all the replies, I've been away for the weekend so couldn't respond sooner. Have spoken to a plumber (can't get hold of the original one) who gave similar advice to that given on this forum and will sort it out for me, I will post a reply when this is done.
RJP said:
Have spoken to a plumber (can't get hold of the original one) who gave similar advice to that given on this forum and will sort it out for me
How immensely rewarding.

Do come back soon with more questions. :rolleyes:

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