shower pump pressure

[jabberwocki]

Just interested if anyone can answer this.
'Do shower pumps vary in pressure' . Reason i ask is that I have a mixershower on 1st floor with pump in the loft. The cold is supplied from the cold water tank and the hot from the hot water cylinder. sometimes the flow from the shower head is very heavy and other times not so.

Been racking my brains as to why. Have checked the pipework and filters and dismantled and cleaned the thermostatic mixer. All is fine. it is not a problem but just puzzles me. Only conclusion I can come to is that sometimes the pump works harder than other times.

Anyone any suggestions. i would love to know why.

 

[ChrisR]

If you get air in, or the HW is too hot, (above 60 ish) it'll drop off a lot.
Usually though it's the pump dying

 

[tamz]

As Chris says probably air. When you say the pump "works harder" if you mean gets noisier it is most likely cavitating.
The last place you want to fit a shower pump is in the loft. Hot probably teed straight off the expansion. Quality

 

[stanboy]

fit a surry flange in top of your hot water cylinder to get rid of air pocket