power shower pump surging

[dazzawiv]

Hi
I have a power shower with a Aquilisa Aquavalve 609.
It has worked fine for years but recently when I move the mixer to certain positions the pump surges. Also, the water pressure has dropped off a bit.
Any ideas about what is causing the problem would be much appreciated

 

[oilhead]

Sounds like a water supply problem. Does it surge when you select cooler or when you select hotter?

 

[Nozzle]

Usually, that's a sign of vortexing on the suction side. Too much flow for the size of pipe and/or not enough static head.

Nozzle

 

[dazzawiv]

Thanks for the reply
The problem is around the mid temperature
If you turn to cold the flow seems ok and the same if you turn it to hot

 

[dazzawiv]

There has been no change to the pipe size or static head.
It worked perfectly fine for the last 5 years until a few weeks ago

 

[Exedon]

Have you checked in line filters are clean?