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Discuss Shower pump not starting for ages in the Plumbing Forum area at

  1. Ahearsum

    Ahearsum New Member

    Hello, hoping someone can help.

    I have a problem with my shower pump (Stuart Turner monsoon S3.0 bar Twin) not starting when the shower is turned on. It needs to be "prompted" by briefly turning on either the sink or bath tap both of which are also connected to the pump.

    This is a problem when the shower hasn't been used for a number of hours (say from morning until evening). But is then not a problem when used late evening after having been used early evening.

    With the pump switched off the water can take as long as 5min to flow through to the shower head. The flow rate is 1.6 l/min with pump off.

    I have enclosed a pdf plan of the pipework. If there is anything anyone can suggest I would be most grateful.

  2. daWilko

    daWilko Member

    Hi - has it always been like this? (or...)
  3. Chalked

    Chalked Plumber GSR

    Your problem is the relative height between the base of your header ta k and the shower outlet..
    The pump , when new would have worked. But as it gets older, the flow switch will get less able to move. So then you have this problem.
    There’s a few cures.
    1. Lift the header tank.
    2. Fit a negative head pump.
    3. Fit a negative head switch ( manual override)
    4. Lower the shower head in to the bath fo start the pump..
    • Like Like x 1
  4. Ahearsum

    Ahearsum New Member

    No. It was installed about 3 years ago .I had intermittent problems like the pump pulsing after having a shower but I lived with it and it eventually stopped . There has been slow starting in the past but not no starting (actually I've never waited the probable 5 minutes for it to start so possibly no starting is over stating it)
  5. Ahearsum

    Ahearsum New Member

    Thanks for your swift reply . Obviously I was hoping to spend no money but hey ho. I'm just a bit puzzled by the water taking several minutes to flow to the shower head when the pump is switched off as if it's leaking away somewhere (no signs of that) it typically varies from 2 to 7 minutes depending on when the shower was last used.

    Could I replace the flow switch or or that just delaying the inevitable?

    I get a little confused between flow rate and pressure. If I raise the header tank I understand I will be increasing the pressure but will I be increasing the flow rate? Is it the pressure or flow rate that's important in triggering the pump? Or both?

  6. jtsplumbing

    jtsplumbing Plumber GSR

    Go for Flow switch first, cheapest option, if that doesn't sort it then need to look into other solutions did it work ok from new or has it always had a problem ?
  7. Ahearsum

    Ahearsum New Member

    Thanks for replying. It was okayish when new. It suffered intermittent pulsing after the shower was switched off but that died down. I should have queried the installation then but ....Curiously, the previous installation, before I put in another shower and changed the pump and pump location, worked fine. The pump (showermate) was downstairs beside the hot water cylinder and shower 2 in the diagram was more or less where it is now. I always understood that it was the distance between the header tank and the shower head that mattered and that hasn't changed.
  8. DevsAd

    DevsAd Member


    Chalked's answer holds all the keys.

    (What a brilliant diagram, by the way :).)

    Almost certainly your issue is essentially caused by the lack of 'head' betwixt your shower head and the cold water storage tank. The very poor flow - delivered by very low pressure - isn't enough to trigger the pump's flow switch. That's no surprise as your current 'head' is less than 1m, which means well under 0.1bar (especially after all the friction in these long pipe runs).

    The 'pulsing' is another classic symptom and is likely caused by a cycle that occurs in situations where the natural flow rate is so poor; the pump finally fires up, quickly & powerfully drawing water out the top of the hot cylinder. But this rapid drawing of water also draws down the standing column of water that sits in the 'vent' pipe which also comes out the top of the cylinder (and which heads up to above the CWS tank). This column of water plummets quickly, reaches a low point and then 'bounces' back up - effectively drawing a column of water back up with it - which momentarily reduces the flow of hot water out to the pump. This might be enough to make the pump's flow switch stop or hesitate for a fraction before firing up again - the cycle repeats. As the pulsing goes on, you likely have a yo-yoing column of water flying up and down that vent pipe - shame it can't be seen...

    As well as gong through Chalked's solutions, it would also be worth checking that the top of the hot cylinder has had a flange (Warix/Warwick or Surrey, I think?) fitted to it to separate the hot water flow from this vent pipe. If it doesn't, that could explain the pulsing.

    Could you post a photo of the top of your hot cylinder, please?

    Could you also post a photo of your CWS, indicating whether there's any room to lift it upwards at all? I'd personally want that as the best solution if possible rather than replacing pumps - it's the most 'natural' solution, tho' it would likely require a good metre extra height to be reliably effective.

    Also as Chalked suggests, try placing the shower head in the bottom of the bath when you start up the shower - see if the pump fires up more quickly. ('Head' is the difference between the stored water level (the CWS) and the outlet. By lowering the outlet height, you are effectively increasing the 'head' and hence the pressure - which then increases flow.)
    Last edited: Feb 10, 2018
  9. Ahearsum

    Ahearsum New Member

  10. Ahearsum

    Ahearsum New Member

    Hi. Thanks very much for the comprehensive explanation. My first time on here and everyone has been so helpful.
    I have enclosed the pics you suggested. Yes I have a flange and no I cant really move the tank much if at all. And the shower heads are fixed so no lowering of those. Negative head pump for me it is then. Anyone in the market for a "preloved" 3 bar positive head pump?!

    Thanks for the diagram compliment. Its kinda related to my job. I've attached another perspective diagram of the plumbing (for entertainment purposes more than anything!). Now if I could just barter some of my 3d visualistation skills for some plumbing services then...




  11. DevsAd

    DevsAd Member

    Wow. How long does it take to run up a diagram like that? And I guess it can then be rotated and viewed from any angle? Nice...

    Yes, there's little extra 'head' height that could be gained there and it would be a gamble on whether it would be enough on its own to ensure good pump performance from your existing pump. So it looks as tho' the most reliable solutions would be as Chalked says.

    As for the pulsing, it's clearly not down to a lack of flange as you have one fitted. A powerful pump like yours will cause a sudden drop in pressure in the cylinder and pipework as it quickly fires up, tho', so I suspect that's still behind that issue; if you can imagine the cylinder walls and pipes being fractionally drawn in (I'm talking a tiny amount) and then springing back out - that can set up that pulsing cycle especially when the pump is on the borderline of being triggered in the first place. That's my theory anyways...

    Let us know what you try and whether it works. A negative-head pump almost certainly will.

    (3 bar is pretty powerful - do you use all that power and flow? If not - if you've always found it 'too' much - then perhaps consider a 2 bar or even less instead; it'll be more gentle on your system and I'd imagine less likely to cause the pulsing problem. But, take the advice of the pro you get in for the job.)
  12. Ahearsum

    Ahearsum New Member

    Thanks again .I think I'll get a negative head pump .If I'd only listened to pro who did all the replumbing and bathroom installations 3 years ago I would have an unvented hot water cylinder which might have been better . A little knowledge is worse than none as they say .
  13. DevsAd

    DevsAd Member

    If you have good mains pressure and flow, then an unvented cylinder gives great performance, and no pump in sight.

    Good luck with your solution - it should be fine.
  14. Ahearsum

    Ahearsum New Member

    Thanks everyone for the advice. I got a negative head pump and everything is fine. Why doesnt everyone get negative head pumps just in case? Its miraculous.
  15. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    extra cost and hope theres enough flow for a pos pump :D
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