Half this amount is out of sight beneath the swimming pools in balance tanks. One drop of water takes two and a half hours to make its way from the pool to the balance tank and back again.
Ian Hall and the DG1 team make sure this water is cleaned through filters and ultraviolet lights to kill bacteria so that the water is fit to swim in.
Fresh water is added from the mains supply daily, as each swimmer removes up to one litre of water from the pool after a swim through their skin and costume.
When water is to be drained from the system, planning needs be carried out with Scottish Water so that local drains do not overflow.