The header tank for the garage and our temporary kitchen, shower and WC is now built and installed on the roof. It is a long box made of OSB boards covered with some left over rubber sheeting to make it waterproof.
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It is only 400mm (just over a foot) high (the water level) but it is 2.4metres long (8feet) and 500mm (1 and half feet) wide!!
This gives us a capacity of about 600 litres to allow us to run the pumping of the tanked rain water in a less frequent on and off cycles. This will reduce wear and tear and noise.