water pressure from taps

[silfox]

I've just moved house and have noticed that every time I turn on a hot water tap the pressure will drop after about 30 seconds to a trickle so I have to open the tap more. this will happen a further two times before it settles into a steady flow. MY boiler is a combination Baxi Potterton Performa 24 eco He, and is about two months old, or so I was told by the previous owners. Also the water will sometimes turn cold for a minute before returning to normal temperature, this happens after its been running for few minutes. The pressure hasn't dropped any and I've checked every radiator for leaks although I guess there wouldn't be any if the pressure is not dropping.
Anyone have any idea what might be causing this?[/b]

 

[ChrisR]

Do all your hot taps do it? Many taps reduce their own flow, for various reasons.
Achieve - somehow(!) a tap drawing about 3 litres/minute hot, and watch the flames. You can expect them to go from high to lower and back, but if the boiler is maladjusted it might be going on and off.

 

[silfox]

Do all your hot taps do it? Many taps reduce their own flow, for various reasons.
Achieve - somehow(!) a tap drawing about 3 litres/minute hot, and watch the flames. You can expect them to go from high to lower and back, but if the boiler is maladjusted it might be going on and off.

The kitchen sink mainly, but the bath tap has also done this from time to times, strangely the bathroom sink tap seems to be fine.

 

[gas4you]

Could be the tap washer in the hot tap expanding and shutting off the flow if it is old