Shower pump set-up?

[Lighty]

Hi all
We've had a perfectly working +ve pressure twin impeller single shaft shower pump for years. A couple of nights ago the hot out connector came free as I was showering!
I've screwed it back on and now it won't run unless on full cold. The plumber has been and can't see anything wrong.
We did however scratch our heads as to where pressure reducing valves should sit? Inlet/outlet/hot/cold/both? It appeared to only have one on the cold inlet previously.
Also, on looking at the pump I can see what must be the magnetic flow switches, I am assuming these should be on the inlet feeds? Would these be effected by not having the pressure reducing valves in the correct place?
Infuriating because I know essentially the pump itself is fine, just suspect it's a flow switch issue!
Any thoughts?
Thx

 

[HERTS P&D]

You have an air-lock.

Andy

 

[Lighty]

Thx Andy, that's what the plumber first thought but after hours running through and changing the hot cold ends on the pump still no better, so we've ruled an air lock out.

 

[HERTS P&D]

Depending on the pump, it might be time to fit a new pump.

http://www.ebay.co.uk/itm/Stuart-Tu..._Bathroom_Shower_Units_PP&hash=item4cfb2a0f0c

Andy

 

[Lighty]

Managed to have a chat with the chaps at pump world who were great. I emailed a couple of pics of the black inserts & what I thought was the pressure reducing valve.

Turns out the red bullet is a magnet that sits in the pump outlet and is lifted by the outflow & activates the magnetic flow switch.

The black inserts sit above it to stop it disappearing up the pipework!

Pump runs perfectly now!