Shower Pump / Flow Issue

26 Feb 2013
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United Kingdom
Hello everyone

We've just fitted a new shower pump and a Scudo bar-mixer shower, and have found an odd issue with the pump cutting in.

First thing in the morning (after a long time not being used), when the bar-mixer is switched on (either fully hot, fully cold, or mixed hot and cold), no water comes out of the head, nor does the pump cut in. I've also tried turning the power off to the pump, and seeing if any water comes out without any pump action at this point, still nothing.

I've since found that if I gently knock on the hot water pipe feeding the mixer, with the mixer turned on, the flow starts, and the pump kicks in as expected. If I switch the mixer off at this point and back on again, it works absolutely fine. Leave it alone for a few hours, and the same thing happens again - no flow, no pump.

I can confirm the following:

- HW cylinder, CW storage tank and pump are located in the loft, with the shower immediately in the room underneath
- We have a Stuart Turner Cyclone 1.5bar twin impeller pump (positive head), situated more or less 1m below the HW outlet from the cylinder, and over 1m below the CW storage
- The hot and cold feeds to the inlets to the bar-mixer are about 1m below the pump, and the shower head itself is probably about 300mm below the pump, literally on the other side of the loft floor
- The HW cylinder has a Salamander S flange fitted at the top, which supplies the pump
- The CW storage tank supplies the pump via it's own dedicated feed (not T'd off any other pipework)

There are no non-return valves, isolators or gate valves cut into any of the shower pipework.

Something else I should mention, when we've finished having a shower, about 2 minutes afterwards, the shower head drips quite a lot - as if it's purging whatever water is left in it - I wonder if this may have anything to do with this issue.

Any ideas would be greatly appreciated at this point!

Thank you very much in advance.
Last edited:
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8 May 2017
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United Kingdom
so no water is coming thru the shower valve when you open the tap . so pump won't start until there is a flow. is your mixer suitable for a low pressure gravity fed plumbing system ? it will have non return valves fitted in the mixer and it seems that they may be sticking or maybe you don't have enough water pressure to open them.

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