Earth Genesis was asked to investigate water use in the bathrooms of a large basement car park where they have 160+ toilets (who’d have thought there were so many toilets in a car park?).

The client selected three toilets to monitor. It should be noted that the existing cistern size was 10 litres and the shattaf was measured at a flow of 20 litres per minute. In this case the toilets were flushing on almost 20 litres! (We calculate shattaf use at 30 seconds per visit).

With three weeks of monitoring completed, the results showed an average of 66 flushes per day. This is a below average flush frequency for toilet flushing but far higher than we would have anticipated for a car park.

Due to the oversized cistern and high flow shattaf, these toilets were seen to be using 77.57 million litres a year.