Hot water from cold tap in new build home

poshphil

Not sure if this is the correct place for it so apologies if incorrect.

We have been in our new build house since just before Christmas. Our ensuite & the bathroom both have mixer taps, but we have noticed when fully on cold the water will run hot for a bit then return to cold. This seems to occur mainly in the evening (probably when we haven't used hot/cold water upstairs for a while).

Having raised this with the house builder they have advised it's because the hot and cold pipes run close together within the floor voids so heat transfer is inevitable and it is possible the water will be warm for the first few liters. Whilst I can see that might be a cause, I don't know whether that is a reasonable thing to be happening and if I should be pushing for a remedy or not, so opinions on this would be welcome.

keith969

It's normal.

Toby09

They shouldn't be close enough to be transferring heat, if they are they should be properly lagged to stop this happening.

Ganga

Well our upstairs bathroom sink tap does this,the house is 33 years old,do you think i should complain to Bellway,s.There is no problem,move on and enjoy your new house.

Jonesya

Ideally the pipes would be insulated with lagging and it wouldn't happen, but clearly they're not and now the house is built I expect they're likely to be inaccessible, running under the floor or in the wall.

Unless you're lucky and the pipes are easy to access to slip some foam lagging around them, well I think you're going to get no where. The builders aren't going to be lifting flooring, floor boards and chiseling out walls to fit some insulation now.

JohnB47

Could you describe your heating system - e.g. is there a cupboard somewhere with a big hot water tank in it and pipes around?

I'm just wondering if the 'problem' could be pipes close together or actually touching in a place where you could get at them to insulate.

If not, I'm afraid that you'll have to live with it.

Have you had a chat with other new build homeowners to see if they have the same issue?

nofoollikeold

Its a fundamental rule of plumbing that hot water pipes are run above cold water pipes to minimise heat transfer. The Water Regulations Schedule 2 Section 9 state that "Any pipe supplying cold water for domestic purposes to any tap shall be so installed that, so far as reasonably practicable, the water is not warmed above 25 degrees C"

Anyone who knows what he or she is doing will run cold pipes below the level of hot pipes, and insulate as necessary. The reason for avoiding heating cold water is to prevent the proliferation of legionella bacteria, whose growth is favoured in temperatures between 20 degrees and 45 degrees Celsius.

You could try pointing this out to the builders. However, I suspect you will have to be very persistent, and possibly point out the consequences of their system causing illness, if you are going to get anywhere.

At the very least write to them, with proof of delivery, and if possible get their written acknowledgement of receipt of your letter.

poshphil

Thank you for the responses. I guess the range of them reflects why I wasn't sure myself!

It is an unvented indirect cylinder so a big tank in a cupboard on the landing.

I paid a bit more attention to it tonight which pushes me more to following up with the builder, as the water coming out is as hot as from hot water tap, ie. too hot to comfortably keep my hand under, and runs that way for probably 20-30s. That seems a bit more fundamental than some heat transfer causing the cold tap to warm up.

The issues raised about access to pipes is valid. They appear to basically go into the floor/wall directly from the cupboard so not much easy access.

southcoastrgi

nofoollikeold wrote: »

Its a fundamental rule of plumbing that hot water pipes are run above cold water pipes to minimise heat transfer. The Water Regulations Schedule 2 Section 9 state that "Any pipe supplying cold water for domestic purposes to any tap shall be so installed that, so far as reasonably practicable, the water is not warmed above 25 degrees C"

Anyone who knows what he or she is doing will run cold pipes below the level of hot pipes, and insulate as necessary. The reason for avoiding heating cold water is to prevent the proliferation of legionella bacteria, whose growth is favoured in temperatures between 20 degrees and 45 degrees Celsius.

You could try pointing this out to the builders. However, I suspect you will have to be very persistent, and possibly point out the consequences of their system causing illness, if you are going to get anywhere.

At the very least write to them, with proof of delivery, and if possible get their written acknowledgement of receipt of your letter.

This is a new build done to a price & tight schedule, the pipes will be thrown in the quickest & easiest route they certainly won't be bothering with which pipe is the highest, is it right maybe not but this is the real world

poshphil

Thought I would follow up on this for anyone finding this thread at a later date. Plumbers from the builders visited yesterday and have advised a valve is needed (second hand information via my wife, she also said they weren't sure exactly where it needs to go), another home on the development has the same problem. Suggests to me some hot water is getting into the cold feed rather than the pipes being warmed, which is the conclusion I had broadly made due to how hot the water was - i'd have accepted water that's a bit warmer but this was essentially fully hot.

jaizan

I presume they will fit a check valve (ie one way) near the tap to stop hot water running up the cold pipe. A very easy job.



Mind you, I'm not quite sure how this goes wrong in the first place, since I don't see how the hot water pressure will be any higher than the cold pressure.

I have seen cold water running back up the hot pipe, when cold is on high mains pressure, hot is at header tank pressure and there is a flow restrictor on the end of the faucet. But not the other way around.