Fitting fibreglass cold water tank

Discussion in 'UK DIY' started by long ironer, May 31, 2006.

  1. long ironer

    long ironer Guest

    Please, what is the correct placement for the Cu exit pipe to the HW
    system from a fibreglass cold water tank? This is a standard
    rectangular shaped tank replacing a galvanized tank.

    SFAIUI a fibreglass tank needs to rest on a platform made from
    (floor)boards carried by joists, rather than just sitting straight on
    joists as per the old one.

    On the old tank the exit CW pipe goes direct out from underneath, but
    I'm getting conflicting advice as to the correct connection point for
    the new one. One suggestion is to copy the old tank (ie from
    underneath), the other is that the pipe should be taken out from the
    side about 50mm up from the boards.

    TIA
     
    long ironer, May 31, 2006
    #1
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  2. long ironer

    BillP Guest

    "long ironer" <> wrote in message
    news:...
    > On the old tank the exit CW pipe goes direct out from underneath, but
    > I'm getting conflicting advice as to the correct connection point for
    > the new one. One suggestion is to copy the old tank (ie from
    > underneath), the other is that the pipe should be taken out from the
    > side about 50mm up from the boards.
    >
    > TIA
    >


    The water regulations G16.6 recommendation is that "Where practicable all
    outlets from a cistern should be taken from the bottom of the cistern."

    The idea is to prevent the build-up of debris in the bottom of the tank.
    Tiny amount of debris that are always present are constantly flushed out and
    therefore don't lie undisturbed at the bottom.

    If your only outlet is the cold water feed to the hot water cylinder, then
    it should be from the bottom of the tank.

    If you have a cold feed for a balanced supply for a shower then this should
    be from the bottom of the tank, and the cold feed supplying the hot water
    cylinder should be 50mm above this from the side of the tank.

    Bill
     
    BillP, May 31, 2006
    #2
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  3. long ironer

    long ironer Guest

    BillP wrote:
    >/snip/


    > The water regulations G16.6 recommendation is that "Where practicable all
    > outlets from a cistern should be taken from the bottom of the cistern."
    >
    > The idea is to prevent the build-up of debris in the bottom of the tank.
    > Tiny amount of debris that are always present are constantly flushed out and
    > therefore don't lie undisturbed at the bottom.
    >
    > If your only outlet is the cold water feed to the hot water cylinder, then
    > it should be from the bottom of the tank.
    >
    > If you have a cold feed for a balanced supply for a shower then this should
    > be from the bottom of the tank, and the cold feed supplying the hot water
    > cylinder should be 50mm above this from the side of the tank.


    TFT that sounds eminently sensible & optimal from a hydraulic
    engineering point of view, but what bothered me, mulling it over before
    posting, was the question of whether a fibreglass tank has the strength
    to take a hole in its base, especially considering the full weight of
    water in the tank.

    (I assume it is made of fibreglass - if not it is some similar looking
    plastic.)
     
    long ironer, May 31, 2006
    #3
  4. long ironer

    Bookworm Guest

    long ironer wrote:
    > Please, what is the correct placement for the Cu exit pipe to the HW
    > system from a fibreglass cold water tank? This is a standard
    > rectangular shaped tank replacing a galvanized tank.
    >
    > SFAIUI a fibreglass tank needs to rest on a platform made from
    > (floor)boards carried by joists, rather than just sitting straight on
    > joists as per the old one.
    >
    > On the old tank the exit CW pipe goes direct out from underneath, but
    > I'm getting conflicting advice as to the correct connection point for
    > the new one. One suggestion is to copy the old tank (ie from
    > underneath), the other is that the pipe should be taken out from the
    > side about 50mm up from the boards.
    >
    > TIA


    As someone who once had the job of investigating faulty Fibreglass CW
    tanks for a manufacturer could I suggest that, under no circumstance
    take the feed from the base of the tank. To do this you would have to
    drill a hole in the base-board, (essential). The weight of the water
    will shear the glass fibre between the fitting and the hole in the
    baseboard. Been there,seen that,hundreds of times.

    I investigated causes of hundreds of leaking tanks most were due to
    incorrect fitting. We had a saying 'If all else fails read the
    instructions'

    I could tell many a tale about faulty installation of CW Tanks.
     
    Bookworm, Jun 1, 2006
    #4
  5. long ironer

    long ironer Guest

    Bookworm wrote:


    > As someone who once had the job of investigating faulty Fibreglass CW
    > tanks for a manufacturer could I suggest that, under no circumstance
    > take the feed from the base of the tank. To do this you would have to
    > drill a hole in the base-board, (essential). The weight of the water
    > will shear the glass fibre between the fitting and the hole in the
    > baseboard. Been there,seen that,hundreds of times.
    >
    > I investigated causes of hundreds of leaking tanks most were due to
    > incorrect fitting. We had a saying 'If all else fails read the
    > instructions'


    instructions? what are those? none came with the tank :-((

    >
    > I could tell many a tale about faulty installation of CW Tanks.


    be most interested to hear them... but meanwhile TFT JIT - only 5 mins
    away from starting & doing job the wrong way when your post popped up
    :))))
     
    long ironer, Jun 2, 2006
    #5
  6. long ironer

    Bookworm Guest

    long ironer wrote:
    > Bookworm wrote:
    >
    >
    > > As someone who once had the job of investigating faulty Fibreglass CW
    > > tanks for a manufacturer could I suggest that, under no circumstance
    > > take the feed from the base of the tank. To do this you would have to
    > > drill a hole in the base-board, (essential). The weight of the water
    > > will shear the glass fibre between the fitting and the hole in the
    > > baseboard. Been there,seen that,hundreds of times.
    > >
    > > I investigated causes of hundreds of leaking tanks most were due to
    > > incorrect fitting. We had a saying 'If all else fails read the
    > > instructions'

    >
    > instructions? what are those? none came with the tank :-((
    >
    > >
    > > I could tell many a tale about faulty installation of CW Tanks.

    >
    > be most interested to hear them... but meanwhile TFT JIT - only 5 mins
    > away from starting & doing job the wrong way when your post popped up
    > :))))


    Story: Had to investigate a tank failure in a refurbished Indian
    Restuarant in Nottingham once. It appeared the owner was so pleased
    with the standard of work that he invited all the tradesmen and their
    wives to a slap-up meal on first night.

    Just sat down to main course when the tank above them burst and brought
    ceiling and tankfull down on them.

    Investigation showed that the Plumber had cut the hole for the 22mm
    Tank Connector with a hacksaw blade very roughly and started a 'notch
    crack' round the fitting in the Polyethelene.

    No payout by manufacturer.
     
    Bookworm, Jun 2, 2006
    #6
  7. long ironer

    Bookworm Guest

    Chris Bacon wrote:

    >
    > They must be very poor tanks not to withstand a head of somewhere
    > between 300 and 500mm. I'd suggest that the weight of unsupported
    > pipework is a more likely cause, combined with poor handling/fitting.


    It is the weight of the water wot does it! 60 gallons @ 8.34Lbs =
    500lbs pressing down on an unsupported area of GRP about 28mm diam
    (hole) less the diameter of the tank fitting (say 25mm). Punches a
    lovely neat hole in a couple of months. Been there,seen it at least 50
    times.

    Good practice with GRP/ Polyethelene or Polypropylene tanks says the
    WHOLE of the tank base should be supported. Make sure the supporting
    timber is sound and free from bugs.

    Once had a maggot hidden in a timber tank support turn in a wood boring
    beetle (Anobium Punctatum). Bored its way upwards through the base of a
    PE Tank. Still got the beetle in a jar somewhere.
     
    Bookworm, Jun 2, 2006
    #7
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