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Shower pumps - positive or negative head

  • 25-06-2014 11:25pm
    #1
    zbluebirdz
    Registered Users, Registered Users 2 Posts: 270 ✭✭


    My knowledge of shower pumps is somewhat hazy/confused :confused:
    I'm hoping a few knowledgeable fellas would be able to clarify a few things ...

    Current setup:
    - Cold water tank in attic
    - Hot water cylinder on first floor
    - Bathroom & ensuite on first floor
    - No water pump(s) are installed

    Shower heads are < 1 metre below the cold water tank and 1 metre above the top of hot water cylinder. They're currently gravity fed.

    I need to have a water pump installed to increase the water pressure for the two shower heads only. All other taps to remain in gravity fed setup.

    Questions for getting a pump for the above setup:

    Which kind of pump would be best to boost the pressure:
    - Positive head?
    - Negative head?
    - Universal?

    Why does a negative head pump cost more than twice the positive head pump?

    Is placement of pump critical?
    - next to hot water cylinder?
    - next to or just below cold water tank?

    If a pump is in the attic, can it cope with extreme temperatures?
    - minus 10c (icy cold winter)
    - plus 40c (roasting hot summer)

    Are low voltage pumps any better than standard voltage pumps?

    Are impeller pumps any better than standard pumps?

    What is the difference between a single and twin pump?

    Am I correct that a submersible pump would not be a suitable unit for supplying pressurised water just to shower heads?


Comments

  • #2
    K.Flyer
    Registered Users, Registered Users 2 Posts: 8,565 ✭✭✭K.Flyer


    zbluebirdz wrote: »
    My knowledge of shower pumps is somewhat hazy/confused :confused:
    I'm hoping a few knowledgeable fellas would be able to clarify a few things ...

    Current setup:
    - Cold water tank in attic
    - Hot water cylinder on first floor
    - Bathroom & ensuite on first floor
    - No water pump(s) are installed

    Shower heads are < 1 metre below the cold water tank and 1 metre above the top of hot water cylinder. They're currently gravity fed.

    I need to have a water pump installed to increase the water pressure for the two shower heads only. All other taps to remain in gravity fed setup.

    Unless both of the shower valves are already plumbed separately back to a common point (e.g. Hot press) you are going to have to either A/ Re-plumb both separately back to the new pump location, or B/ Pressurise everything, including taps and toilet cisterns from the pump.
    zbluebirdz wrote: »
    Questions for getting a pump for the above setup:

    Which kind of pump would be best to boost the pressure:
    - Positive head?
    - Negative head?
    - Universal?

    The installation of a Positive Head pump should be perfectly fine.
    A brass bodied negative head (also called Universal) would be a belt and braces set up.
    zbluebirdz wrote: »
    Why does a negative head pump cost more than twice the positive head pump?

    A brass bodied Stuart Turner Positive Head pump is approximately two thirds the price of a Negative Head. This is because there are more components fitted to the pump to enable it to function in a Negative Head situation.
    zbluebirdz wrote: »
    Is placement of pump critical?
    - next to hot water cylinder?
    - next to or just below cold water tank?

    In the set up that you have described above, you would usually use a positive head pump, usually located in the hot press if there is space available.
    zbluebirdz wrote: »
    If a pump is in the attic, can it cope with extreme temperatures?
    - minus 10c (icy cold winter)
    - plus 40c (roasting hot summer)

    - minus 10 is below freezing which can cause the body of the pump to crack and leak as well as other un-protected pipework. Which is why the hot press location is preferred as the warmer temperature of the space helps protect from freezing.
    The pump is WRAS rated to carry water up to 65*C
    zbluebirdz wrote: »
    Are low voltage pumps any better than standard voltage pumps?

    Personally only ever fitted one, so I cannot say, I have always fitted Stuart Turner and the occasional Grundfos.
    zbluebirdz wrote: »
    Are impeller pumps any better than standard pumps?

    What do you mean by standard?
    zbluebirdz wrote: »
    What is the difference between a single and twin pump?

    Am I correct that a submersible pump would not be a suitable unit for supplying pressurised water just to shower heads?

    A submersible pump pressurises the water through a single pipe in the same way as a "single" pump does. Neither would suit your requirements as you need to boost the pressure of both the hot and the cold to your showers.
    Single pumps are used to boost hot and cold water pressures in homes, but this would be a different plumbing set up to the one you have.


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