It shuts off water to a branch or fitting so it can be maintained without closing the whole supply.
Isolating and Mixing Valves for Plumbing Runs
A local shut-off valve can spare the rest of a property from being without water while a tap is serviced. MacBlair lists brass and chrome isolating valves in 15mm and 22mm sizes, plus a thermostatic mixing valve on its water-supply-valves page. These do different jobs and should not be treated as interchangeable.
An isolating valve closes a section of supply pipe for maintenance. A thermostatic mixing valve blends hot and cold feeds to control outlet temperature. Match each fitting’s size and orientation to the pipework and check the intended water duty against the product specification.
Place any local valve where it can be reached after installation, especially beneath a basin or near a tap. If the whole water supply must be shut off, locate the main stopcock first. The wider tap range can be considered alongside the valves when refreshing an outlet.
Water Supply Valve FAQ's
Measure the existing pipe and match the connection size. Do not select by the size of the tap alone.
It blends hot and cold water to control the temperature delivered at an outlet or group of outlets.
Not necessarily. A local valve and main stopcock serve different parts of the water system.
Yes. Put it where it can be operated and inspected when maintenance is needed.