Shower pump giving up after 5 minutes?

Hi all,

More misery from SJ I'm afraid... I have had a pumped shower for yonks and it has always worked fine. CW is fed from a separate take-off from the tank in the loft, HW from an Essex flange from the HW tank in the airing cupboard - never any problems with pressure. All pipework to this pump is 15mm.

At the weekend I fitted a Surrey flange to the HW tank as I will eventually be installing an Aqua Lisa in the other bathroom. The feed off the Surrey flange goes about 1 metre, then a maintenance valve (full flow), then another metre into the loft, and is then capped off for now. Obviously, to fit the valve I had to drain a little bit of water from the hot tank, as well as emptying the cold tank to install a new tank connector for the cold feed to the Aqua Lisa. All new pipework is 22mm.

Since fitting the Surrey flange, which should have made no difference to the Essex flange as the Essex flange is lower down on the tank, the 'old' shower works fine for about 4 or 5 minutes (pump kicks in, thermostatic mixer sorts itself out, and loads of lovely hot water comes out of the shower head). Then, and this is where I'm stuck, the water pressure drops off to the same as it would be without the pump, and the pump stops working. After about another 5 minutes, it all works fine again for a few minutes then cuts out!

To my meagre brain-cell this would appear to be caused by a drop in pressure in the cold tank not supplying sufficient cold water and/or head to the hot water to operate the solenoid on the pump? Or have I got that totally wrong? (nothing new there, then!) When I am in the shower at silly o'clock in the morning the rest of the household are doing the decent thing (sleeping) and not drawing off any water.

The mains feed pipe to the CW tank is 15mm with a 14 year-old stop-cock in the airing cupboard. I thought maybe the stop-cock was mis-behaving and not filling the tank quick enough, but I checked and it all seems OK (we have a water softener on the system, but I'm not sure if that is plumbed before the feed to the loft or after, so if it is after I guess limescale could be a problem although like I said the tank does appearss to fill up OK).

Is this possibly something to do with a) the Surrey flange, b) me draining part of the system, or c) none of the above? It justs seems very coincidental that everything was tickety-boo before I fitted the Surrey flange...

Hope someone can help. Many thanks, SJ

have you checked the tank in loft when this happens ?
maybe the ball valve is not opening fully to fill the tank.

It sounds like you may have air locked the system; although the flow switches may initially kick the pump in, an air lock can reduce flow to the point where there is not enough pressure to trigger the pump flow switches & the pump shuts down.

Did you bleed the system at the pump when you refilled it? What sort of pump is it? What route do the pipes take from the pump to the shower? I assume your h/w cylinder is still vented via the new Surrey flange? Shouldn't make any difference if the cylinder is vented but have you tried bleeding trapped air from the new capped off pipe on the Surrey flange.

seco services said:

have you checked the tank in loft when this happens ?
maybe the ball valve is not opening fully to fill the tank.

Click to expand...

Yup - ball valve is fine, no air in the system either, but it does appear that when I cut the new take-off from the CW tank that some swarf might have managed to escape down the feed pipe... Went to check the pump last night, but the gate valves are not holding up and the water came p!ssing out! As such, will try again tonight but will have to drain the tanks again first (

Thanks all for the advice so far...

What happens if you open another hot tap when the shower is running?

If there is any restriction in the cold water feed to the hot cylinder, such as a failed gate valve, or bits of loft insulation or other 'foreign bodies' drawn down the outlet from the cold storage tank, the pump can start drawing air down the open vent.
The shower pump would stop when the water level in the cylinder drops below the outlet, as it has nothing to pump.

If the cold feed is restricted, I would expect the flow to other hot taps to fail a little before the shower cuts out

TicklyT said:

What happens if you open another hot tap when the shower is running?

If there is any restriction in the cold water feed to the hot cylinder, such as a failed gate valve, or bits of loft insulation or other 'foreign bodies' drawn down the outlet from the cold storage tank, the pump can start drawing air down the open vent.
The shower pump would stop when the water level in the cylinder drops below the outlet, as it has nothing to pump.

If the cold feed is restricted, I would expect the flow to other hot taps to fail a little before the shower cuts out

Click to expand...

Other hot taps are not affected, and hot water continues to go through the pump to the shower head, just without and pressure... As such I'm guessing that feed from CW tank to HW tank is OK. Also, the water comes out VERY hot, possibly indicating that HW supply is fine but CW supply is restricted?

All I can think is that when I drained the CW tank, I allowed swarf from the new tank entry hole to enter the CW feed pipe to the pump. I will be able to check this later, but as the gate valve on the CW supply pipe appears to have failed I will have to drain the system first (and fit a new maintenance valve whilst I'm at it). Hopefully, I will then just be able to clean the CW intake filter, flush through the CW supply pipe again, remove any swarf/debris from the CW tank (properly this time) and everything will be tickety-boo once more...

If not, I will just have to plumb in the new Aqualisa temporarily so I can scrap the existing pumped system, then take it out again when I rip out and refurb the en-suite in a few weeks time.