Cold/warm water from hot tap, and cold taps run warm

DarkHorse

Some advice please from any plumbing experts out there.

I have a hot water problem, whereby the hot water on some taps runs nice and hot, but on others it is cold.

We have a mains pressurised system in the house since a loft conversion 5-6 years ago, and have no cold water tank any-more. The boiler is working fine, and the mains pressured hot water tank is nice and hot.

We do also get a problem with the cold water sometimes running hot on some taps for 5-10 seconds.....really strange.

This all started about a month ago, but seems to have been getting steadily worse. There have been no changes to the plumbing, so I cannot pinpoint what could suddenly cause this problem to occur.

Today I thought I would try to resolve the problem by draining the entire system (hot system, and heating), but this has not changed anything, and the problem continues.

One thing that I have noticed as a temporary solution to get hot water from one of the taps that refuses to run hot in the bathroom sink, is to turn on the offending mixer sink tap (it will run cold), and then turn on the thermostatic bath tap (which also runs warm, not hot), and then the sink tap goes hot.

Any advice on what could be causing this and a cure?

tigeress289

Just walked in and been a nightmare day plumbing. First thought is mains pressure (cold) is higher than hot from boiler. Can you try and reduce incoming mains and give it a try? Need to eliminate one by one. Will get my thinking cap on and get back soon.

tigeress289

Does the hot run OK on single pillar taps? How is the cold supply on all the taps, mixers or not?

keystone

tigeress289 wrote: »

......... been a nightmare day plumbing....

We know that - there's been water pouring out all over the place all day long. Don't say it was all you.

Cheers

brig001

My thought would be that a mixer tap is allowing the hot and cold to mix and my money would be on the thermostatic bath tap. Does it have non-return valves on it (some have them built in)? If you can't tell, can you isolate the water to that tap and then see if every other tap in the house behaves properly?

HTH,
Brian.

tigeress289

Hi Keystone, I never want to see an IKEA double sink with the cheapest trap ever. The customer did not take advice to change it and I get all the AGG. Not only that ,they fitted it and forgot I needed to get to the cold and hot feed, which seems my fault. Happy days!!!

Canucklehead

Hi.

Do you have a thermostatic mixing valve supplying the bath and BASIN tap? AKA, TMV.

Bath mixer might have a thermostat problem of it's own.

Is the hot water pressure, in general, lower that it used to be?

Maybe the inlet filter on the unvented cyl is blocking.

You have had it serviced haven't you? They are supposed to be serviced every year, but usually don't get looked at until they go wrong.

You have a hot pipe running very close to ,or touching, a cold supply. This gives a slug (not a snail) of warm water from a cold tap.

GSR.

DarkHorse

tigeress289 wrote: »

Does the hot run OK on single pillar taps? How is the cold supply on all the taps, mixers or not?

Unfortunately we dont have any single pillar taps, but I have switched off the cold on the isolator valve on the mixer taps, and the problem persists.

tigeress289 wrote: »

Can you try and reduce incoming mains and give it a try? Need to eliminate one by one. Will get my thinking cap on and get back soon.

Have tried this, but again no success.

brig001 wrote: »

My thought would be that a mixer tap is allowing the hot and cold to mix and my money would be on the thermostatic bath tap. Does it have non-return valves on it (some have them built in)? If you can't tell, can you isolate the water to that tap and then see if every other tap in the house behaves properly?

This is a very good idea. I will pop the bath panel off tonight to see if I can see if there is a non-return valve or a isolator to test this theory.

Canucklehead wrote: »

Hi.

Do you have a thermostatic mixing valve supplying the bath and BASIN tap? AKA, TMV.

Bath mixer might have a thermostat problem of it's own.

Is the hot water pressure, in general, lower that it used to be?

Maybe the inlet filter on the unvented cyl is blocking.

You have had it serviced haven't you? They are supposed to be serviced every year, but usually don't get looked at until they go wrong.

You have a hot pipe running very close to ,or touching, a cold supply. This gives a slug (not a snail) of warm water from a cold tap.

Just a thermostatic valve supplying the bath and shower, the sink is on it own mixer tap.

I get the feeling that it could well be the bath thermostatic valve playing up.

Hot water pressure seems to be the same as the cold.

I haven't had the unvented cylinder serviced ever......was never advised to, but again this could be the problem.


Looks like I may have to call a plumber out to take a look at the system.......can anyone recommend decent, reliable plumber that covers Guildford?

tigeress289

How is the kitchen sink? Have to say you are doing OK eliminating different things.

Ectophile

Getting warm water out of the cold taps for a short time just means that the cold pipe is run close to a hot one (perhaps a central heating pipe).

Are you allowing enough time for hot water to run through? It can take several litres of water if there's a long pipe run.

DarkHorse

Just to keep you updated, I still don't have a solution to the problem.

I contacted a plumbers merchant that I have used in the past for parts so that they could recommend a plumber, which they duly did.

He came around the other day for a quick look, and was puzzled why this is happening, and confirmed that it is all very strange.

He is coming back on Thursday to start a full diagnosis, and has a few possibilities that he will try.

Hopefully it will be a simple solution in the end.....I will update!