3 Fabricating the Hot Water Tank
3.1 Hot Water Tank Design
The tank is comprised of an inner barrel with an outer protective casing:
55 gallon metal drum casing (890 high x 580mm diameter) with lid.
35 gallon plastic barrel tank (780 high x 500mm diameter) with lid.
3.1.1 Insulation
Two rolls of 2mm fiberglass Termo-flex insulation (approx 1800 wide x 900mm high each) are
wrapped around the inner-tank and one inside the outer drum. A cylindrical piece of
polystyrene foam is used to cover the inner tank lid for extra insulation: approximately 25mm
thick x 56mm diameter.
3.1.2 Inner tank hole positions for inlets1
(bottom of the tank‟s inside to hole centre)
Cold water feed – 100mm
Hot water out – 540mm
Solar Flow (hot) – 460mm
Solar Return (below it) - 95mm.
3.1.3 Outer tank hole positions for inlets
(from floor outside the tank to hole centre)
Cold water feed – 130mm
Hot water out – 570mm
Solar Flow (hot) – 490mm
Solar Return (below it) - 125mm
!! Note: these positions are approximate. They are based on the Inner tank inlet positions. The
exact outer tank hole positions will vary, according to the tank height difference; based on the
tank thickness, insulation and the off-cuts positioned between the two.
Alignment between the two tanks is easier to achieve by drilling the outer-tank first, although
this method may vary inner-tank hole positions.
Plumbing to the tanks is carried out with ½” fittings. The holes for these inlets should be made
0.5mm larger than the fittings. Holes made in the inner tank for inlets must be sealed to
prevent leaks. The outer tank forms a protective casing; inlets should be sealed to prevent
ingress of rain-water (leading to rust on the inside of the drum.)
1 Note: These positions are thought to be optimal for the inlets but they are yet to be tested.
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