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Photo of a plastic open drum tank
Plastic open drum water tank.  Note that the opening is slightly smaller than a steel drum opening, which makes it harder to draw water using a watering can.   However it was easier to set up as, being plastic, I was able to place it directly on the ground.  I used 50 mm PVC piping for the inlet and outlet fittings.

This tank was set up in a friend's garden.