3.1.5 Cold Water Inlet: float valve and shut-off valve
The cold supply should have a shut-off valve on the outside of the tank. It also features a float
valve inside the cylinder, to shut off the supply when the tank is full (like a toilet cistern.)
Supplied with male threading, its connection substitutes for the nipple which passes through
the inner tank wall in the list above. It is usually supplied with an HG washer; an extra rubber
washer is fitted on the inside of the tank, and a rubber and an HG washer on the outside.
It comes supplied with the float connected to an attachment „arm‟. If the arm is too long for the
tank, it can be replaced by an 8mm screw. The inlet is low down, to prevent mixing with the hot
water higher up, so the float is cut from the arm and reconnected with a small link chain,
(approximately 450mm for the valve to close when the tank is full: 20mm below the top of the
tank). A sacrificial anode would prevent corrosion caused by dissimilar metals (e.g. the chain).
The cold water inlet is plumbed to the outer tank as follows:
(Nipple from the inner tank) shut off valve nipple adaptor pipe
3.1.6 Weather proofing
The outer drum should be painted black with anti-corrosive paint before assembling the inlets.
Each hole in the outer drum should be protected against rain ingress with a 76 x 76mm patch
of black rubber. A small piercing is made in this material and the pipe passed through with a
snug fit. The patch is attached around the hole in the tank with silicone on the sides and top;
leaving the bottom unsealed allows any water ingress behind the patch to escape. The outer
tank‟s underside should be drilled with several holes to allow drainage in case of rain ingress.
3.2Hot Water Tank Fabrication
3.2.1 Making the holes in the inner and outer tanks
1) Mark the holes in the outer drum. This should aim to correspond with the positions of
the holes in the inner tank. Allow a height difference (between inner-tank inside and
outer tank outside) based on the inner tank thickness, and the insulation and wooden
off-cuts you will position between the two.
2) Drill the outer drum using a hole saw for metal. These should be just large enough for a
coupler (female) fitting to pass through. Remove burrs with a file.
3) Place the inner tank inside the drum to mark the inner holes.
4) Drill the Inner tank holes. „Spade‟ drill bits for wood can be used. Start small and
gradually increase the hole until the nipple (usually ½”) fits snugly (aim for Ø of hole
0.5mm larger than the fitting.)
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