Bath Tap Temperature

[Leaky123]

Hi All, I have an odd problem, we moved into our house about 5 years ago and have always had a problem where the bath tap runs from scorching hot to luke warm after it's been running for a minute, despite the heating being on all day, this process can be repeated after switching off for about a min. I think the whole heating system is the original one from about 30 years when the house was built. It's a conventional gas boiler (not combi) and for some reason we have a large combination hot water cylinder, despite it being a 4 bed house with loft (no separate cold water tank). The other taps, en-suite shower, around the house all seem to run hot water continuously with no problem. Any suggestions regarding the problem would be welcome, thanks.

 

[Riley]

Is your bath panel removable? I suspect that you have a thermostatic mixing valve under the bath which potentially is not working correctly or is set too low. This is a safety device installed avoid people scalding themself

 

[Harvest Fields]

What make and model of boiler do you have and what make and model of cylinder?

 

[Leaky123]

What make and model of boiler do you have and what make and model of cylinder?

What make and model of boiler do you have and what make and model of cylinder?

I'm not at home to check the exact makes, I believe it's a Potterton, 1980's gas boiler and here's an image of the cylinder.

 

[Leaky123]

Is your bath panel removable? I suspect that you have a thermostatic mixing valve under the bath which potentially is not working correctly or is set too low. This is a safety device installed avoid people scalding themself

Hi, I don't think that's the case because we had the bath and taps replaced about 2 years ago.

 

[Riley]

I don’t understand why if the installer was installing to regulations he should’ve installed one ??

 

[Riley]

Failing that do you have a thermostatic mixer on the bath? That could’ve failed

 

[Leaky123]

I don’t understand why if the installer was installing to regulations he should’ve installed one ??

Oh, really. Ok, I'll check that then, thanks.

 

[Burger]

I don’t understand why if the installer was installing to regulations he should’ve installed one ??

I don’t think he needs to as they usually only apply to new builds or a material of change, which from my interpretation is like a barn conversion etc.

 

[Burger]

Hi, I don't think that's the case because we had the bath and taps replaced about 2 years ago.

There could be a restriction, eg a washer that may be worn on the tap, or a flexible pipe that is twisted.

 

[Riley]

Shouldn’t make it run like warm though. Are you actually going to check for a TmV or just assume there isn’t one

 

[Harvest Fields]

Is there a mixer on that cylinder?

 

[Leaky123]

Is there a mixer on that cylinder?

I'm sorry, I don't know, what am I looking for? Does the photo above help?

 

[Riley]

No photo

 

[Riley]

So I’d you don’t know what you’re looking for how can you say it’s not there. May need a pro

 

[Harvest Fields]

Get yourself an engineer out mate. Probably for the best.

 

[SimonG]

Tmv only on new. Replacing an existing doesn't need one. Do you have a shower or anything similar. Could be mains cold back feeding through cooling hot.

 

[Leaky123]

No photo

The photo was further back in the thread. I have arranged for a plumber to visit tomorrow but just wanted the heads up on what the problem might be.

 

[Riley]

None of us should assume but you are right. But we don’t know what was there before the bath swap but as the OP doesn’t know what they’re looking for it’s all a bit finger in the wind

 

[Riley]

Based on that set up I would agree with Simon thinking cold backfilling

 

[Leaky123]

Tmv only on new. Replacing an existing doesn't need one. Do you have a shower or anything similar. Could be mains cold back feeding through cooling hot.

There is a separate mixer shower above the bath taps which seems to be fine.

 

[Riley]

Could be thermostatic though so is capable of dealing with the cold Mains

 

[Shower Engineer]

There is a separate mixer shower above the bath taps which seems to be fine.

In that case it could be the hot NRV in the mixer shower that is causing the problem.

 

[SimonG]

Goosed check valve. Changed a shower last year. All outlets in bathroom not very hot. They spent a fortune on visits to fix the combi. I was referred to change shower and swap taps. Phoned me after to tell me the water had never been so hot in the bathroom. All down to shower.

 

[Coby kenny AGUILAR]

I'm not at home to check the exact makes, I believe it's a Potterton, 1980's gas boiler and here's an image of the cylinder.

View attachment 38195

Check under bath and see if you have on of these.
Google Image Result for https://cdn.aws.toolstation.com/images/141020-UK/800/18520.jpg

If you don't have a TMV send a picture of bath taps and could you try get a clearer image of the cylinder and pipework later on, take a step back and include as much pipework as you can

Does anyone else see two pumps? Maybe a thermal store with a mixer on the side...

 

[sammathias]

I don’t understand why if the installer was installing to regulations he should’ve installed one ??

Do you install a tmv everytime when fitting a bath??

 

[Riley]

You don’t have to but on the rare occasion that I have done baths in recent years I have just from a safety perspective because they tend to be elderly customers

 

[Leaky123]

Thanks for all the advice and prompts. I’ve worked out there is a TMV on the cylinder pipework and think this might be the problem. I’ll let you know how I get on.

 

[Harvest Fields]

Thanks for all the advice and prompts. I’ve worked out there is a TMV on the cylinder pipework and think this might be the problem. I’ll let you know how I get on.

How did you figure that out?

 

[EvilDrPorkChop]

Isn't it a thermal store, hence the two pumps? Rather than just a traditional cylinder.

 

[ShaunCorbs]

Yep thermal store