One of my jobs this summer is to replace the loft tanks
and the supporting woodwork, since it has sagged so much
that it is almost touching the plasterboard.
Screwfix sell standard cold water tanks in 25g and 50g
capacities. I'd prefer a 25g since it's easier to handle.
Are there any regulations which state what capacity it
has to be?
The limiting factor is usually how much water you want to draw from the tank
at any one time. If your bath is fed from the cistern, it also tops up the
hot water cylinder and you like a deep bath, you may find that 25 galls
means that the water slows to a trickle part way through filling. If your
hot water comes from a flow boiler and the cold water is all mains fed, the
cistern is only acting as a reserve for your WC cisterns and 25 galls will
be fine. Personally, I fitted two 25 gallon cisterns, linked at low level
(about 50mm off the bottom) with a large bore pipe, with cold water drawn
from that pipe. That was partly to spread the load more widely around the
loft and partly because of the size of the trapdoor.
If you have any gravity fed showers, now's the time to build a trestle and
increase the head pressure to them (raise the store tanks as high as is
Don't be tempted to insulate below the new tanks though!
In last house I replaced split large round tank with two 25g tanks connected
by two 28mm pipes at bottom. These were chosen as easy to get though the
limited loft hatch size without having to fold, bend, squeeze etc leading to
possible future damage.
I thought the advice was to ensure a "flow" of water from entry into the
tank to exiting from the tank.
Presuming only one ballcock, your setup might lead to areas of still water
which might encourage stagnation?
Just mentioning the point.
Running a full bath, which I like, virtually empties both (I have a large
bath) so most of the water changes daily. The only problem I do get is that
the fill is less positive since fitting the second tank, so sometimes the
ballcock starts a bit of water hammer. I can relieve that by opening one of
the cold taps attached to the mains, but permanently correcting it is on the
to do list.
Hmmm... I'm not convinced Colin: If your daily consumption of water is more
than the capacity of the tank, can you also ensure that you use all of the
"old" water before any of the "new"?
When I replaced my cold water tank a few years ago I took the advice mentioned
here and fitted a "Torbeck" valve.
About a year ago I got persistent water hammer. A swift email to the company
and they sent me some new components for the valve - methinks there was
a design problem with the original.
So if your problem is via a Torbeck valve then consider this.
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