Home Design Guides: Bathroom, Energy and water management, Shower
In most plumbing setups, it takes a while for hot water to reach the hot tap when it's turned on. Cold water diverters recycle the cold water which would otherwise pour down the drain in this time.
Water-producing bathroom fittings in Australia need to comply with basic water-efficiency standards. As a part of the WELS scheme, they are rated and given a label that shows how efficient they are.