Salamander Pump malfunctioning

[John2Frustrated]

I have installed a Salamander ESP 50 CPV negative head pump. The hot water supply from the pump is slow or almost non existent and the pump sounds like it is full of air bubbles. When I flush the air out it runs ok for one or two showers and then repeats the problem. When I take the shower taps off the pump delivers perfectly at full volume. I have replaced the shower taps with different ones but the problem persists. I have checked the pipewprk both before and after the pipe and there are no blockages. The supply from the hot water system is via a warix flange and the complete system is exactly as the manufacturer's installation manual. I have installed automatic air vents in the pipe work between the pump and the shower unit. I have contacted the manufacturers and told them the symptons and they insist the pump is not the cause of the problem. I could do with changing the pump temporarily to see if that solves the problem but the pumps are nearly £300 to buy. Any body got any good ideas other than buying a new pump? John2Frustrated

 

[seco services]

what taps have you fitted ?
give us a pic.

 

[John2Frustrated]

Thank you, Seco. The original shower tap was a Grohe 1000 BIV shower bar. I have replaced it with a bog-standard off the shelf type shower bar costing a quarter of the price of the Grohe. This has made no difference to the performance of the shower.