When rainwater, the easiest to obtain, is insufficient, the combined system automatically kicks in with reclaimed water, the second most costly source. When there is not enough reclaimed water, the tap water system, the most costly, kicks in to help.
當最容易取得的雨水不足時，整合系統會自動將次高成本的中水補充進來；當中水不足時，成本最高的自來水系統又會自動補充到中水系統。