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Discuss Shower pump woes in the Bathrooms, Showers and Wetrooms area at

  1. KnickersKnackersKnockers

    KnickersKnackersKnockers New Member

    Dear Exalted Ones

    It is my sincerest hope that somebody might be able to help me with this one, as it's doing me swede in...
    I have recently installed a Stuart Turner Monsoon Single 1.5 bar pump (secondhand, admittedly) in order to boost pressure to my bathroom, in particular a new shower (thermostatic valve mixer/bath filler). The pump is feeding the whole bathroom - not ideal, I know, but no workaround available.

    Cold is mains, hot is delivered to pump via 22mm (PEX), one elbow involved on the supply side, two on the delivery side of the pump.

    Full bore isolating valves to bath/shower have been fitted, with a non-return valve on the hot, then (admittedly not full bore) 22mm flex hoses to both hot and cold.

    The pump is fed from a Salamander S-flange (Surrey type) which I installed, with the 28mm venting to the header tank (head approx 2.5 metres), and also feeding the (gravity fed only) HW to kitchen tap - which is upstairs of the cylinder (bonkers I know - old council flat)

    The 1 inch vent originally went to a 1 inch x 2 x 3/4 inch (all imperial) reducer, down to the bathroom and up to the kitchen HW (in half inch) and vented in 3/4, so I cut the original 3/4 feed to the bathroom and capped it off (a few inches dead leg only) and connected the pump discharge on to the bathroom feed. Simples!

    (you'd think...)

    Problem is, the hot tap in the bathroom - which is teed off before the shower - runs for about 5 seconds then starts coughing and spluttering, clearly indicating cavitation (but eventually runs like a demon); and the shower is sort of ok, but sometimes pulses, with the only rectification being to leave the basin HW on a little, as if that tells the pump that it's definitely expected to be pumping! The basin taps are single pillar, so there's no way that the hot and cold could be communicating with each other there at least.

    Other info that might clarify is that the ancient, ancient (brazed on!) valve between the header and the cylinder is letting by, and for all I know might never be fully open either, so incoming pressure could conceivably be down.

    Do you think it is likely that the above-mentioned ancient valve is only half open, so that the cylinder is not filling up quickly enough to keep pace with the demands of the pump? Or is it conceivable that the dead leg that I have introduced is somehow causing some kind of air intake?

    Stuart Turner came back to me with some - in my view - wholly wrongheaded advice, essentially telling me that the pump I have is unsuitable, and that what I should really be doing is buying a shiny new one from them. How astonishing...

    All and any feedback (and I'm a sound engineer) most warmly welcomed

    Photos by way of elucidation to follow, if I can work out how to make it so

    Thank you! You are legends!

    Monsoon ID Label.jpg

    Ancient cock!.jpg


    Pump supply 2.jpg

    Pump supply.jpg

    Salamander flange.jpg
    Last edited: Dec 11, 2018
  2. king of pipes

    king of pipes Trusted Plumber GSR

    Few errors there bud you can't feed the pump off the cold main its not allowed in the water regulations i am afraid, it needs to be gravity fed from the cold water storage tank and will then be equal pressures on the hot and cold that's why your having problems with pressures , also you should not have used pex off the cylinder either and the salamanders not piped right read the instructions your going to have all sort of problems here you could possibly blow a seal on the pump and have a flood so I would get it sorted double quick see if i can find a pic of how it should be ? Kop

    • Agree Agree x 1
    Last edited: Dec 11, 2018
  3. Pickwickpick

    Pickwickpick Plumber

    What's wrong with how the salamander is fitted, apart from the pex coming of it? Its not something I've ever fitted or even come across in real life.
  4. king of pipes

    king of pipes Trusted Plumber GSR

    See attached

    • Like Like x 1
  5. Ben-gee

    Ben-gee Plumber Top Contributor!!

    KOP, it’s a single - he’s only pumping the hot. (not the mains).
    I agree no plastic that near tank, but can’t see anything else obviously wrong.
    Spluttering start indicates air, obviously, how are pipes run? Any up/downs, inverted loops?
    The other possibility is you need a negative head pump, I admit I’ve got confused as to which floor does what in your house! Or of course the pump is already dodgy, as often 2 nd hand ones are. Other point is what is your mains pressure? Hot should match it if you have mixers, I’ve used this set up on several occasions, but usually 3 bar pump for whole house hot.
    • Agree Agree x 1
  6. YorkshireDave

    YorkshireDave Plumber

    First things first.

    The surrey flange installation def concerns me. It looks as if the normal supply output dips down as it leaves. IF it does, or even if its horizontal, you will get air into the pump supply. The air off the top of the cylinder needs an easy path out otherwise it'll just be sucked out by the pump.

    The valve in the supply to the cylinder is easy to check. It's a BS1010, so disassemble it and make sure its fully openable. It's not like a gate valve as it uses the same internals as a std multi-turn tap so it should be fine.

    How did you evacuate all the air from the pipework in the first place? I take it you turned the pump off opened the shower and let it all bleed through till no more spluttering occured?

    How do you know the pump works fine? Which type of pump did ST advise?
    • Like Like x 1
  7. KnickersKnackersKnockers

    KnickersKnackersKnockers New Member

    • Creative Creative x 1
  8. KnickersKnackersKnockers

    KnickersKnackersKnockers New Member

    Thanks so much everyone for your replies and advice

    KOP - Ben-gee is right: I'm not pumping the mains (I know better than to do that), just the stored HW

    I'd have thought that mains fed cold/gravity fed hot is precisely the sort of arrangement whose shortcomings a single impeller pump was designed to overcome - is that idiotic?

    The S-valve has been fitted exactly as per the manufacturer's instructions (and it's not the first one I've fitted either, just the first to have been such a nause.)

    Ben-gee - yes, the layout of the apartment is a bit of a headf***!
    Essentially it is as follows: in the front door (landing, leccy and storage cupboard), down a half staircase (as in 7 treads) to living and kitchen area with CWS at head height in the kitchen; do a 180 and down again (7 treads) to airing cupboard and bathroom, then down again (7 treads) to two bedrooms, then another 180 and down again (7 more) to exit. Even more mental than that is that some of the adjacent apartments are the other way round! (my five year old daughter calls it "Daddy's upside down house".)

    Please tell me what is wrong with using PEX as I have. It was just cheaper, and - aesthetics and 'best practice' considerations aside - I cannot for the life of me see how plastic pipework can be a contributory factor in a pump's failure to deliver water to a tap, or indeed an outlet of any kind.

    The pump could of course be faulty, but then how does that explain why it runs like a dream to the shower as long as the basin tap is opened a little (or the mixer is set so as to deliver scaldingly hot water)?

    Yorkshire Dave - I'm sure you're right, and I did suspect that possibly the vented outlet should be inclined upwards, although I have no idea why. No installation guide that I have ever seen has stipulated that this be done, and no installation diagrams I have ever seen have indicated this either (I do get that they are schematic, but FFS...)
    And - given that this is evidently so important - would it not be a nice idea for a flange manufacturer to make a fitting whose top outlet was set at 45 degrees, rather than horizontal?

    The kitchen HW/vent pipe doesn't dip, but is definitely horizontal; so please, kind sir, could you explain to me how I introduce an upward inclination to that pipework so that it still mates with the fittings that it needs to meet squarely? I'm not a plumber, but I'm pretty darned handy (slap on the wrist re use of PEX notwithstanding)

    Thank you all!
  9. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Turn the water mains off open a cold mains tap then try the hot tap again same thing happens or not ?
  10. king of pipes

    king of pipes Trusted Plumber GSR

    My mistake bud sorry was a bit early not got any answers for ya .
  11. KnickersKnackersKnockers

    KnickersKnackersKnockers New Member

    Hi Shaun, and thanks for your reply, but I'm afraid that I have no idea what you mean at all. Do you mean at the shower valve? And what is meant by "same thing happens"? As I indicated in my original post, the spluttering - for want of a better word - happens at the single pillar hot tap on the basin, which is teed off before the shower, so it is not just the usual shower nause that I am inquiring about
  12. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Turn the mains water off eg your mains cold water stop tap

    Open a mains water tap eg kitchen cold

    Then go open your problem tap does it do the same as before
    • Like Like x 1
  13. KnickersKnackersKnockers

    KnickersKnackersKnockers New Member

    I can isolate the (mains) supply to the kitchen cold, and the (mains) supply to the bathroom and toilet cistern cold, but individually only via stopcocks to each
  14. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    So you don't have a mains water stop tap that turns everything cold water mains off?
  15. KnickersKnackersKnockers

    KnickersKnackersKnockers New Member

    Negative. Correct.
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