Hot Water From Kitchen Cold Tap

[Colin Stoker]

Hi All

Just joined this excellent Forum and I hope someone can give me some advice on a problem I have in one of my rented flats.

Yesterday, my tenant sent me a text saying that hot water was coming from the cold side of the kichen sink mixer tap. I went round today and this was indeed the case. I checked other taps and there didnt seem to be the same problem. Its an unvented mains pressure hot and cold system with the hot being fed via a Santon Premiere Plus 210E cylinder. The kitchen tap itself has two separate valves.

It is definately not the tap itself because the pipes feeding the tap both get hot. However, if the cold tap is left on for long enough, it eventually runs cold. The cold water temperature after turning on the cold tap is therefore cold, tepid, hot, tepid then cold. This takes place over a period of approximately three minutes. Once running cold, and the cold tap turned off, it takes a while for the problem to repeat itself, but it does after about 20 minutes.

This is not something that has been getting increasingly worse - it just happened yesterday apparently.

Any ideas?

Colin

 

[Plumbstar Tom]

it sounds like some where along the run the cold pipe is sited above the hot and probably touching it leading it to heat the cold pipe up

 

[Meady]

If that was the case though why would it only just start doing it??

 

[Chalked]

If that was the case though why would it only just start doing it??

New tennant, running heating hotter or longer.
other option is a non return valve fitted to a shower mixer may be sticking, or cylinder piped wrong.

 

[kris]

My first though was back pressure from somewhere but the cold pressure will usually outway the hot at every turn , and also you say it takes 20mins to heat up then run tap for 3mins then it runs cool, that would probably cancel back pressure unless its only when someones using the cause ie shower or other mixer tap. this is one of the reasons a check valve will go on the coldmain going into hot water cyl, me personally id feel the cold at the cyl, make sure its not getting hot and that eliminates that then the same with any other mixer taps or showers to see if you find it ,,, only other thing there wouldnt be an electrical device in a cupboard or a battery fan or something battery operated (anything that would give off heat stuck ON in a cupboard next to pipe, its a long shot but worth while checking , even the tennants putting piles of towels over the hot and cold would accumulate heat and transfer slowly, could be a few things good luck mate

 

[village idiot]

Most certainly a non return valve issue, me thinks
An already present one is now faulty (see post by chalked), or decide on a location and fit one (bath mixer, shower mixer, etc).

I am actually going to fit one tomorrow to a rented flat. Old tenant has left, new tenant now says tank in loft keeps overflowing even though she has checked and no water is being discharged from valve in tank?

I have decided on two options,
1) Change the sink mixer taps, oR
2) Fit a NRV to hot pipe feeding sink mixer tap, which is what I will do as it is the cheaper option

 

[Colin Stoker]

Thanks all for your help.

I've had a problem before with a dodgy mixer tap which was internally letting by the higher pressure mains cold water so it backfilled the hw cylinder leading to over-pressure and setting off the prv to discharge. However, I can see no reason why the mains water supply to the sink is getting so hot - I cant see it as conduction from the hw pipe as nothing has been changed nor do I think it is the cold pipe being in a hot or covered place as the water temperature is too high.

Tenant has been in for 4 years. Its all electric so no lphw primaries. Water coming out cold tap is same temperature as the hot tap. Installation is 10 years old and hasn't been changed or modified at all. Can it be anything to do with the cold water combination valve fitted on the supply to the cylinder?

It's doing my head in :smilewinkgrin: