Low flow from power shower ?

[Jonno2001]

Hi, newbie to this site, but recommended by a friend

I installed a Showerforce easiboost (1.5bar) power shower pump a few years back now, coupled to a Gainsborough thermostatic mixer unit etc. But really since installation the shower takes a good few minutes for the hot water flow to settle. In the mean time the head splurges and often the pump stops for a second or so in the same way as the thermostatic valve being shut ? But after say 2 minutes the flow stabilises and the pump noise settles down and quietens.
I recently stripped the valve down to check there was no restrictions and equally replaced the shower head in case that was restricting the flow.
More recently, i've found that if i start the shower but open the wash basin hot water tap fully there is initially little or no flow from the tap, leave it 5 seconds and the flow returns, and hey presto the shower works fine too.
I'm no expert but understand that this is the effect of an air lock, but what would be the best cure ideally to prevent the air lock in the first place ??
Any help or suggestions most welcome.

Regards, and happy new year
John

 

[bab]

I'm sorry to say that the istallation may have a design fault compiled with low quality products ending in poor performance ,but thats only an opinion with out visual backing. The supply piework to the pump & from the pump to the valve must always prevent air from collecting.

 

[Jonno2001]

ummmm, i think i've read somewhere since that i should take the hot water supply from as high up as possible, where as i've just used the old bath tap hot water supply, so the t-off is pretty low to the bottom of the shower basin ?