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

 

[ShaunCorbs]

Low water pressure???

 

[Gasmk1]

is there a mixer tap or shower could be draing the cold water through one of them

 

[Harvest Fields]

What boiler is it and what Is the hot water flow rate.

 

[Riley]

I did think mixer tap or shower but it’s so strange that it runs perfectly for 10 minutes and then goes cold but only when the cold bath tap is on. Boiler is a new Biasi combi ( not fitted by me I hasten to add). Flow belts out Of both the hot and cold taps And hot does need to be throttled back to achieve piping hot

 

[Harvest Fields]

Could the cartridge be closing slightly when bothbtaps are on?

 

[Riley]

Cartridge on what mate?? There are no thermostatic mixers?

 

[Riley]

Sorry just realised I didn’t say that the hot and cold taps are completely separate.

 

[Harvest Fields]

Sorry just realised I didn’t say that the hot and cold taps are completely separate.

No worries. What is the flow rate on the tap after he 10 minutes?

 

[Riley]

Identical doesn’t drop off. If full open then easily 15/16 litres if throttled back to achieve piping hot then 10/11 litres at good temp

 

[Harvest Fields]

Could he flow switch on the boiler be cutting out?

 

[Riley]

As I said mate when cold is off hot water tap runs constantly hot at a good temperature. It’s only when the cold tap is on the hot runs cold about 10minutes later

 

[Harvest Fields]

When it goes cold does the boiler cut out or stay alight?

 

[Riley]

Stays alight it’s really bloody weird. The only recent change is the new bath taps but these really are nothing special contract variety

 

[Harvest Fields]

Very strange. Worth getting BIASI out and you being on site at the same time??