Strainer and non-return valve

A strainer is a mesh or perforated screen fitted at or before a meter's inlet to catch sand, scale and debris. A non-return valve lets water flow in one direction only and stops water draining back from the property into the main.

A strainer keeps grit away from the meter's moving parts. A non-return valve stops reverse flow, which can turn some registers backwards and can let water from inside a property flow back into the main.