existing pump, new shower, no water!

Wonder if I can pick your collective brains? (Esp kevplumb!)

Having a new shower fitted (by 'professionals') - twin control thermostatic concealed valve, where before there was just a combined bath tap/shower mixer. Have a gravity fed system, not got combi boiler and have Showermate 1.4 bar twin pump which supplies the bath taps (and now the new shower).

The problem is that when I turn on shower, no water at all flows and pump doesn't start. However, if I turn on the hot or cold bath tap momentarily, this starts the pump and the shower will then work on it's own. However, leave it for an hour or so and the problem returns. What I don't get is that before the shower was fitted, even if the pump was turned off, I got some water out of the taps - but just a dribble. So reckon it must be something to do with the shower not the pump?

The pump doesn't have non return valves, so I reckon the ones in the shower should be left in? Also I've noticed that the incoming and outgoing pipes to the pump is 15mm, but this then changes to 22mm. I've also taken the shower hose off, but no difference

Any thoughts on what might be the problem??

I'm starting to get a bit whiffy and will need a shower soon....
SB

Someone has suggested that it is air in the system that is causing the problem and that if the shower supply pipes are raised up above the height of the pump (which is under the bath) this should solve the problem.

Whadda you think?

SB

It's not some sort of safety device in the shower that cuts off the shower if there is insufficient water pressure ? In the thermostatic shower adverts it's often mentioned as a safety feature. If so, you need do something so that the gravity pressure reaches the shower enough to overcome the safety device - make sure any service valves etc are fully on.

sounds as if the nrv's are a bit strong for the gravity head

ie turn tap on pump starts overcomes the resistance

no water flow no pump

Dal5band - thanks for idea, but my shower doesn't have these.

Kevplumb - hello! - is an nrv a non return valve? (don't forget I'm from the world of electricity not water!)? I've just spoken to a different person at the manufacturer who suggested I remove them from the shower. Is this something I can tackle myself (obviously isolate supply first...).
I didn't fit the shower so don't even know what they look like, but can see from the instruction book where the housings are located.

Help - I feel like a real DIY'er!

SB

yeah you usually need a set of allen keys and isolate the water supplies or drain down first

OK kevplumb - I'm going to give it a go. If you see someone riding the crest of a wave down the A23, you'll know I forgot to turn off the supply!!

SB

what make/ model of shower

Hmmm - have taken off the housing - I assume the valve is the white plastic bit held in with a circular copper ring (which it looks like you can squeeze the ends together to remove it?) If I do this will the valve come out? Then do I just screw the housing back in? Or would it be easier to nip out and get new housings with no valves??

Good job I didn't decide to become a plumber...

Thanks in advance

SB

Oops, missed your latest post. Anyway, its a Hudson Reed/Home of Amber twin control thermostatic shower valve, if this is of any help

SB

keplumb - you are a genius!

Removed nrv's and all is well. If I wasn't already hitched to Mr Sparkybird, I'd propose!!!

Cheers

SB