2 pumps on 1 hot water tank

Discussion in 'Plumbers' Talk' started by GordonK, Nov 12, 2017.

  1. GordonK

    GordonK Member

    similar to another post someone just asked but I’m in a 3storey house with my immersion tank on middle floor. Coming out of the top it goes upstairs and there is a t-connector in the airing cupboard on the middle Flor coming out which feeds the lower floors.

    I installed a pump in the top floor next to cold water tank and linked up a pump to both to feed my new en-suite on the 2nd floor.

    Everything good ...

    Then decided that the downstairs hot water pressure sucks and decided to fit a pump onto the downstairs feed from the immersion tank... fitted it up and it works fine...

    I’ve now noticed that the downstairs pump comes on whenever I run the hot tap from the other pump ... I can understand that is down purely to the fact the water pressure reduces on the hot circuit so it thinks hey I need to pump hot water and therefore it goes off...oddly enough the other pump upstairs doesn’t come on if I run water downstairs...

    2 questions really.

    1. Does this seem like it’s working as expected
    2. If not will this cause issues with the downstairs pump I had fitted?
  2. First question - if you live in a 3-storey house, why is the hot pressure pants on the ground floor? It should be awesome...
  3. GordonK

    GordonK Member

    You tell me...

    cold pressure is fine but all my cold feeds come from mains (this is an old 1910 edwardian ex B&B)

    The pressure anywhere off the hot tank direct isn't great .. up or down... I suspect that the pipes running downstairs may be throttled with smaller bore pipe but pulling up all the boards and walls to examine that isn' an option so it is what it is..hence the eed for a pump ...that in itself isn' that uncommon.
  4. I don't quite follow your setup - where each item is installed, and on which floor. All this detail is important.

    I also don;t understand why the hot flow pipe out the top of your 'immersion' tank (do you mean hot cylinder?) goes up a floor before teeing off to supply the downstairs. That seems convoluted to say the least. The flow pipes should run the most 'obvious' course - tee off above the cylinder and then come down to the floor level of the cylinder where the pump is then installed.

    You fitted the initial pump up in the loft area near the cold storage tanks?

    I suspect, if you want useful advice on here from plumbers (I ain't one...), it would be worth sketching out what you have in a diagram, and see what folk have to say.

    (I thought most booster pumps worked on 'flow' rather than pressure, so I don't know why a reduction in pressure would trigger your second pump to fire up.)
    GordonK likes this.
  5. The Teach

    The Teach Active Member

    What does the downstairs circuit consist of ? There could have been an alternative solution,retro fitting multiple pumps is very diy.

    There will be some movement of water in the downstairs pump when the other pump is operating,sometimes enough movement of water to trigger the flow switch.

    solution,fit one suitable pump in a suitable position to pump the necessary hot outlets.

    or you can get a few plumbers to visit they will be able to see your installation (we cant) and give estimates on getting the best hot water flow in your property.

    should be an easy fix.

    GordonK likes this.
  6. GordonK

    GordonK Member

    17D7AC01-0359-401D-B163-E40FF0F7736A.jpeg See if this makes any sense of it ...
  7. Dr Bodgit

    Dr Bodgit Well-Known Member

    You'd be best off with one pump feeding both.
    GordonK likes this.
  8. GordonK

    GordonK Member

    I don’t disagree but that’s not going to happen easily without some major pipe work change .... let’s assume I can’t ...
  9. The Teach

    The Teach Active Member

    you could have an essex flange fitted to supply hot water to the pump on the first floor,it will be an independent supply just to that pump only.

    It may work depending on the rest of the plumbing layout,on site investigation is required.
  10. GordonK

    GordonK Member

    For the record it was fitted by a plumber ...

    I'm just not happy with it as it doesn't seem right ... apart from not being aesthetically pleasing is there an issue with it as per my original post is the question.... he seems to think its ok..
  11. Dr Bodgit

    Dr Bodgit Well-Known Member

    Are these pumps positive or negative head?
  12. GordonK

    GordonK Member

    No idea... how would I know?
  13. Dr Bodgit

    Dr Bodgit Well-Known Member

    What are make and models are these pumps then? A positive head pump will turn off when the shower is turned off, whereas a negative head pump will keep going for a bit in order to build up pressure before turning off.

    Reason for asking, and why I made my comment above regarding using one pump, is that I was considering a very similar setup in my gaff. I had the plumber round and he immediately said this could cause issues:
    - with one pump going, it may cause issue with the second pump, presume as the hot water pressure is reduced at the second pump and some pumps don't like that
    - when we looked at where the first pump would be situated, it won''t fit in the ideal location at the bottom of the hot water tank. Raising it up is possible, but he warned that if raised too high I would need a negative head pump. I would expect you pump on the 2nd floor would be a negative head pump.

    The smacks of needing an expert plumber on site to advise you.
    GordonK and Deleted member 33931 like this.
  14. Makes and model numbers of both pumps?

    The top pump must be working at close to negative head, but seemingly it's working ok whatever type it is.

    I don't understand why the new pump fires up, at least not if it's flow-switch operated. Does it keep on running for as long as the other pump is on? If so, I guess it must have a pressure-switch instead; the other pump reduces the hot pipe standing pressure, so that's enough to trip the new pump.

    Solution? Fit a flow-switch type :)

    (That's all guess work...)
    GordonK likes this.
  15. The Teach

    The Teach Active Member

    The best advice.

    Diy has its limitations,many home insurers do not cover any diy plumbing work although exchanging tap washers is allowed.
    GordonK likes this.
  16. GordonK

    GordonK Member

    Ok ..both pumps are Stuart Turner ..

    Highest one is a 3 bar twin which works with positive or negative head.

    Lower next to cylinder is a 2bar single positive head ...

    If i run downstairs tap then the top pump remains off... .. if I run the upstairs hot the lower pump comes on ..
    Deleted member 33931 likes this.
  17. The Teach

    The Teach Active Member

    Get a plumber that understands pumps,a simple alteration could be all thats required.
  18. Dr Bodgit

    Dr Bodgit Well-Known Member

    I'll echo that.

    My thoughts - the upstairs one is likely a positive head pump, it builds up pressure before turning off so is less susceptible to turning on should there be a small pressure drop. The lower one is a negative head pump and will turn on when it detects a flow of water. It might be that the lower one needs to be replaced with a negative head version, but I'm just guessing.
  19. GordonK

    GordonK Member

    That's not the case.. I advised the pumps earlier...
  20. Dr Bodgit

    Dr Bodgit Well-Known Member

    Brain fart, let me try again...

    My thoughts - the upstairs one is likely a negative head pump, it builds up pressure before turning off so is less susceptible to turning on should there be a small pressure drop. The lower one is a positive head pump and will turn on when it detects a flow of water. It might be that the lower one needs to be replaced with a negative head version, but I'm just guessing.

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