I have a Powermax 155 which is about 7 years old. When I turn the shower or a hot tap on full there is a loud "clunk" from the boiler and the water cuts off. I then have to turn the shower/hot tap off and turn on in stages, a small step at a time, eventually it seems to settle down and I get a reasonable flow, although if I try to push my luck and go a bit further then the "clunk" happens again and I am back to square 1. Any help would be greatly appreciated.

Rogh, May 2010

i have a powermax 155 when i turn on the hot water the flow is great for a few seconds and then dies down and if i turn on another tap at the same time the flow is non existant any thoughts

DARREN, May 2011

blending valve

tim, May 2010

Sounds like a scale problem inside the tank, most likely a large piece of scale has come adrift and is restricting the flow. 7 years on a powermax is pretty much at the end of its life span even if it is serviced regularly.

boiler bill, May 2010