As opposed to concrete cisterns, due to their lower weight plastic tanks can usually be moved without heavy equipment and therefore avoid major damage in the excavation pit and in the garden. This is especially important if you are installing a rainwater utilization system in your garden at a later date. Another advantage of a plastic tank is that it is easier to clean, since concrete tanks have rough inner walls where dirt can accumulate more easily. There is also the risk that particles of cement leaching out might pollute the rainwater and in the worst case cause damage to the pump. Calcium secreted from the concrete of the cistern can also actually make the initially lime-free rainwater "hard" and thereby shorten the life of your washing machine.