Shower pump issue please help

Hi, I have recently installed a shower pump. I have run a dedicated cold water supply from the cold tank and a dedicated hot water supply via a Surrey flange of the top of the cylinder. My problem is if I turn the bathroom or kitchen tap on and off really fast the pump cuts in, sometimes once and sometimes it will pulse every couple of seconds until I turn it off on the wall. I assume its air and have taken the head of the shower and let run but this still happens. If I turn the output shower valves off it still happen but if I turn the input shower valve off it does not so I assume the problem is in the hot water pipes that feed the taps around the house and not the new pipe work I've put in for shower. Would fitting a non return valve to the top of the hot water cylinder before it tees off to the vent pipe and taps stop this? Is that even aloud? Hope I've given enough info and any help is much appreciated. Thanks Chris

Air trapped after pump. (quite common on new install, hot temp sky high, no flange fitted or fitted round wrong way)

Close the pump hot inlet valve and I bet it stops. If this does look for any possible air trap after the pump I.E. up and over pipework and vent it.

Don't fit non return valves on the system especially on vent pipework, they may get over the problem but not a direct cure and will only slow gravity water down/cause restriction.

If I turn the output shower valves off it still happen but if I turn the input shower valve off it does not

Click to expand...

If this is so, it's doubtful that air is trapped after the pump, assuming the valves are on the pump hose connections.

No a check valve in the location you describe is not allowed by regulation, it would not function as vent pipe.

a check valve on the hot supply to the shower only would be permitted, it may even resolve to problem.

Perhaps a pic of the pump and its pipework and the valves would be useful?

usually a non-return valve on the hot outlet or as close to the hot outlet as you can will provide enough back pressure on the pump to stop the flow switch kicking up and activating the pump momentarily.

regards