Pressure loss on hot tap

[Briggscroft]

Hi just wondering if any one can help. The problem i am having is when using my mixer tap in the kitchen or the hot tap in the bathroom for hot water (both are new taps) the flow is good to start with and then slowly dwindles away needing to be turnd up again to increase the flow. I have a combi boiler which is a baxi duo tech 33he which was installed about 2-3 months ago. At the time the plumber who is corgi reg informed me my mains pressure was very good due to a new mians being put in. He knew this due to the type of plastic pipe which feeds the house. Thanks for your time Briggscroft.

 

[TicklyT]

I had similar on a basin tap a few years back... The hot water used to almost stop as the tap body warmed up, needing the tap opened further to maintain the flow.
Close the tap, and after five minutes it used to start dripping as it cooled down.

I put it down to differential expansion - the jumper expanding more than the tap body as it warmed up and cutting the flow, then contracting again as it cooled down until it started to drip.

 

[ChrisR]

It took me about 4 attempts to get to the bottom of some mixers doing this. The washers had squashed and become larger diameter, which is common, but in so doing were blocking the water outlet from that part of the tap, which was sideways. So a slight expansion on heating was all it took. As both mixers were the same make they gave the same symptom, though it seemed to be the supply. Solution was to trim the washers' diameter slightly

 

[Briggscroft]

Just to clarify there is one mixer and one basin tap doing this but i have a mixer tap on the bath which does not. could it be the washers that need triming on two completely differant makes and types of taps? both these taps have been replaced within the last 3-4 months