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]

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 ??

 

[Riley]

No only since the taps were replaced. Unfortunately tenant can’t remember what sort of taps were there

 

[Riley]

Hello mate by the way

 

[Harvest Fields]

No only since the taps were replaced. Unfortunately tenant can’t remember what sort of taps were there

If that’s the case have you got a pic of the taps. I would just change them.

 

[Riley]

They are just bog standard contract at no-frills at all

 

[Harvest Fields]

They are just bog standard contract at no-frills at all

If that’s the only thing that has changed mate. I would by as set of cheap and nasties and whack them on to see if there is a difference.

 

[Riley]

It might come to that but there’s just no logic to it

 

[Harvest Fields]

It might come to that but there’s just no logic to it

But that’s the only thing that has changed. (According to the customer)

 

[townfanjon]

No only since the taps were replaced. Unfortunately tenant can’t remember what sort of taps were there

This one gets better , its a belter !

 

[Riley]

Ha ha agreed. Tenant is not bad to be fair, pretty switched on but can’t really remember the previous taps as they were changed literally the day after they moved in. I think New taps it is

 

[PETE 123]

antiscald device in tap maybe operating if one fitted to that type

 

[plumbandplumber]

Is the dhw pipe out of boiler still hot when the water from tap has gone cold?

 

[Riley]

Certainly is

 

[Riley]

No antiscald

 

[ShaunCorbs]

its not new build is it?

 

[townfanjon]

Not teaching to suck the old eggs and all that , but have you tried running the hot tap with the heating off and seeing if heats going around HTG circuit , it is a Biasi after all

 

[Riley]

Ha ha it’s a valid point and may well be worth I try. It just seemed so odd that tap runs for 10-15 mins then goes Stone cold

 

[Riley]

its not new build is it?

No mate

 

[peter0504030201]

is your boiler pressure gauge set higher than 1.5 bar , The system may be slightly over-pressured , the increase in temperature results in an increase in pressure, this might push it over its limit and again it will cut-out ?

 

[Riley]

The boiler doesn’t cut our

 

[Gasmk1]

then if all else is ok it must be the bath taps. can you put your temp sensor on the hot flow from the boiler and watch that