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 wrote:
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.

That's OK.


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.

The latter suggestion is best.

"long ironer" wrote in message
ups.com...
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 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" wrote in message
ups.com...
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.

The argument for putting the take-off in the base is that any sediment will
be flushed out of the cistern. The argument for putting it 50mm up the side,
is that any sediment will settle to the bottom and stay there.

Unless this is the supply the primary circuit of the heating system (it is
not entirely clear from your post) the regulations require the outlet to be
fitted with a service valve, which may be easier to fit with a side
take-off. It also tends to be easier to check a new side connection for
leaks once you have done the job. The regulations also require any storage
cistern to have a cover that excludes light and insects, adequate insulation
and an overflow that excludes insects. The bits you need to achieve that are
usually sold as a water byelaw kit, although the water byelaws were replaced
by the Water Supply (Water Fittings) Regulations 1999.

Colin Bignell

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 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 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.

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.

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.

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 wrote:
Chris Bacon wrote:
[someone 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.

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.

Fortunately, hydraulicals don't work like that! Must've been poor
pipework.