plumbing mystery!

[reebok22]

Problem is a kitchen mixer tap where the hot is only warm - unless you run the bath tap on hot or cold upstairs at the same time - then the water from teh kitchen tap is piping hot! The downstairs cloakrm tap is fine.
There is a house pump that kicks in for pressure.
Have changed the ceramic cartridge in the mixer - no difference. Any suggestions, please?

 

[plumbnuts]

Sounds like a case of unballanced pressures. Is the tap a single lever mixer tap? What can happen is that if the mains pressure is very good it can overpower the hot feed even if pumped. This will result in the cold main mixing with the hot water making it warm. This can be overcome by fitting non return valves to the hot and cold supplies to the kitchen taps or changing the taps for one that has seperate supplies within the tap to the spout. ie not mixing the water in the tap body.
Steve

 

[reebok22]

Many thanks for your advice. I'll give that a go.

 

[Bernie2]

Can't understand why water authorities ever changed the By-Laws and asked only for nrv's on the cold main, rather than as formerly, insisting on all mixers being bi-flow.

They should have insisted on both. Perhaps then we would be getting less people asking about bi-flow problems.