Service valve
In plumbing · also called Isolating valve
A small valve on the pipe to a single tap, cistern or appliance, so that one outlet can be turned off without shutting off the whole house. Many are quarter-turn: the slot or lever lines up with the pipe when the valve is open and sits across it when closed. Turning one off and then opening the outlet shows whether it has worked.
Using Service valve in a plumbing system
Updated
A distinction worth remembering
A service valve makes local maintenance possible without necessarily shutting the whole supply. Its condition, accessibility and the system layout matter; a slot in a valve body is not proof that it has fully isolated the downstream pipe.
Questions to take further
- Does turning off the stop tap empty the system?
- No. Pipes and storage vessels can still contain water, and separate systems may remain supplied. Isolation and draining are different operations.
Sources
- Skills England: plumbing and domestic heating technician — The systems, materials, planning and customer responsibilities in the England occupational standard.
- GOV.UK: Approved Document G — Guidance for England on hot-water safety, including stored hot water; guidance is not itself the legislation.
Where Service valve fits in the learning path
The Isolation, Hot Water Safety and Simple Repairs section covers these topics:
- Isolating and Draining Down
- Hot Water Safety
- Everyday Plumbing Repairs
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1. Read it in context
- Isolating and Draining DownIsolation, Hot Water Safety and Simple Repairs
- Everyday Plumbing RepairsIsolation, Hot Water Safety and Simple Repairs
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A valve that shuts off the cold water supply to a building or to part of it. Most homes have an internal stop tap where the supply pipe comes in, often under the kitchen sink, and another outside near the boundary, usually under a small cover. Knowing where the internal one is, and checking that it turns, is the first step in dealing with a leak.
Stop tap
Read the Stop tap entryCompare related terms
Open a meaning to compare its role with Service valve, or follow its full entry.
Stop tap — Stopcock
A valve that shuts off the cold water supply to a building or to part of it. Most homes have an internal stop tap where the supply pipe comes in, often under the kitchen sink, and another outside near the boundary, usually under a small cover. Knowing where the internal one is, and checking that it turns, is the first step in dealing with a leak.
Read the Stop tap entryIsolation
In plumbing, turning off the water to the part of a system you are working on, then proving it is off by opening an outlet and checking that the flow stops. Isolate as close to the job as possible, with a service valve where there is one and the stop tap where there is not, and drain the section down before opening it up.
Read the Isolation entryBefore you start: some plumbing work is regulated or notifiable
Some water fittings work needs notice to, and consent from, the water supplier before it starts. Check the rules where you live.
Gas work is for competent workers covered by a Gas Safe registered business in Great Britain. Northern Ireland has separate gas regulations. Do not work on gas pipes or appliances yourself.
In England, installing an unvented hot-water system over 15 litres is notifiable building work: use a competent installer registered with a competent-person scheme, or tell building control before work starts. Leave this work to a suitably skilled person.
Wales, Scotland and Northern Ireland have their own water and building rules; check which apply before work starts. Electrical connections belong with an electrician.
This guide does not qualify you or make you competent, approved or registered for plumbing, gas or unvented work.
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