Shower pump

[gf35]

I have recently updated my shower to one of these over head showers that has an additional body spray and a detachable shower at the bottom of the unit. when I first installed it, the shower worked fine. It has now been 2 weeks since a last tried it as I haven't tiled the area, and when I went to use the portable shower no water came out, I tried turning on the over head shower and nothing worked, after a few minutes the pump kicked in and the shower started to work, pressure was not as good as before. I left the shower a little while and tried a again and the same problem occurred except this time the once the water started to flow the pump then turned off stopping the water. I have tank in my airing cupboard which has a pump at the base which pusses the water back into the loft then down into the shower, I have check all connection and no leaks. Some has suggested to put non return valves in? please help?

[The Builder]

I'm wondering about this pump in the airing cupboard. Do you have very low mains pressure?
If so .......... a mains pump would give extra pressure, but not extra flow (volume of water).
Lack of flow could mean the shower "runs out" of water and creates air locks.
Just one of the things that might cause this.

[gf35]

Hi, thanks for the reply. The old shower worked well with the pump, I was looking at the hower last night and noticed that when you use just the hot water the shower works fine but the cold seems to have low pressure as the water flow reduces when you introduce cold water through the shower?

[The Builder]

Hard to tell from here gf. Some showers handle "unequal" pressures better than others. Check out the technical data that came with the unit. It should give guidance on required pressures and flow rates.

[AlBags]

I'd say there is a poss. that water siphons back to cylinder. If so, use NRV's.
Is the pump plumbed directly from Cyl with flexy 22mm hoses?
What size is inlet cold fill pipe from tank to cylinder? This will connect into the base of cylinder. For you this needs to be at least 28mm (or 2x 22mm) Separate feed to pump from header tank for cold (preferably 28mm)