Weird hot water issue

[Riley]

Scratching my head a bit with this one. I don’t know if anybody has come across this before. Bath in a property has very basic nonceramic taps when she runs h & c, hot runs cold after about 10 mins. It’s off a combi boiler sonoy a lack of water. When she run just the hot tap it runs continuously hot.

Hope somebody might be able to offer a pearl

 

[Riley]

No I’m just trying to find a solution. It’s almost like there is a crossed pipe somewhere but all other outlets work fine

 

[ShaunCorbs]

Does the boiler stop firing ? When both are open?

 

[Riley]

No mate carries on firing as normal

 

[Riley]

And if I open another hot outlet it runs hot as normal. Albeit the flow reduces because two hot taps are open

 

[Harvest Fields]

Does the boiler stop firing ? When both are open?

Asked that earlier mate.

 

[Riley]

It’s a proper head scratcher isn’t it

 

[armyash]

Interested to read the outcome of this.

 

[snowhead]

It's almost as though whoever fitted the new boiler and or taps, also fitted a TMV (under the bath) which is playing up.

 

[Riley]

Nope thought TMV but nothing there

 

[Allgoode]

Hi,
You could put a check valve on the hot supply to the bath to eliminated cross-flow.
might fix or will allow you to rule out the issue for little cost.
Cheers,
Andy

 

[Riley]

Thanks for the idea but on single taps what will a check valve do?? Am I missing something

 

[Vee]

Are there any other thermostatic fittings in the property. I had an instance where a broken shower mixer was affecting flow in a similar way. Also check the rating of the boiler DHW flow rate as it may only be capable of raising it through 35dgC @ x flow and pressure. If either flow or pressure drop off the boiler may not be able to cope.

 

[Harvest Fields]

Good shout on the shower mixer. But he said that the pressure doesn’t alter at all on the flow through out the ten minutes

 

[Riley]

Yeah and the boiler continues to fire. It’s almost as if the hot water is diverting elsewhere but it’s not

 

[townfanjon]

Yeah and the boiler continues to fire. It’s almost as if the hot water is diverting elsewhere but it’s not

Ehup pal , the big one ... has this happened since the new boiler was fitted ??