The Water Supply (Water Fittings) Regulations 1999 set out the requirements for water fittings. For the public water supply, the regulations aim to:

Defra says approved specifications as a way of showing compliance with relevant regulations - the water companies are responsible for enforcing the regulations.

Water Regs UK are funded by the water companies to promote compliance with the regulations. It also administers WaterSafe, a UK wide register for installers and RPZ testers, and, on behalf of some water undertakers in England and Wales, the Water Industry Approved Plumber Scheme (WIAPS). which supports UK water companies to develop and enforce the water fittings regulations and byelaws, which help protect the quality of public water supplies and prevent water waste.

Water fitting specifications approved by the regulator set out the legal requirements as a way to comply with the regulations; some specifications are referred to as Test Code Sheets (TCS).

The specifications published on the Water Regs UK website apply in their current form. Water Fittings Regulations’ refers to The Water Supply (Water Fittings) Regulations1999, The Water Supply (Water Fittings) Regulations (Northern Ireland) 2009 and The Water Supply (Water Fittings) (Scotland) Byelaws 2014

From 6 May 2027, the updated specifications set out below will apply:

Specification on the Prevention of Backflow 

WC Suite Performance Specifications 

TCS 1511-2 Flush Rate 

TCS 1512-12 Wash of Bowl 

TCS 1611-16 Liquid contaminant, dye retention 

TCS 2212-3 Vacuum, Dimensional 

TCS 2213-15 Dimensional 

TCS 2213-21 Joint below critical water level 

TCS 5011-7 Warning pipe and overflow provision 

TCS 2213-20 Dimensional and internal overflow compatibility  – this is a new specification that will apply from 6 May 2027

From 6 May 2027, specification TCS 5011-5 Measurement of dimension, will no longer apply.