Hot tap on bath will only run (with cold water) when the boiler is off

Hi. Providing the central heating system is fully working and it’s only that particular tap I’d say there was a fault inside the tap. I would then give a price for repair or replacement.

Hi I take it you have a combi boiler so when the boiler is off the tap will only have water that is cold combing out of it. Also the reason the bath tap and only the bath tap is lower pressure then the other taps is because the bath tap is 3/4 tap so it causes what we call a reservoir and makes the pressure less.then the last thing it could be is a faulty tap that will either need stripping down and fixing or a tap reviver putting in hope this has helped