Stopcock
| Stopcock | |
| Type | Valve |
|---|---|
| Also known as | Stop tap, stopvalve |
| Function | Isolates the water supply to a property or a section |
| Regulatory basis | Water Supply (Water Fittings) Regulations 1999, Schedule 2 |
| Typical positions | Boundary or highway chamber, and inside the premises |
A stopcock, also called a stop tap or stopvalve, is a valve that shuts off the flow of water to a property or to part of its plumbing. Most properties in England and Wales have at least two that matter: an external one in a chamber at or near the boundary, and an internal one where the supply pipe enters the building. The Water Supply (Water Fittings) Regulations 1999 set requirements for stopvalves and other water fittings in Schedule 2.[1]
Function and position[edit]
The internal stopcock isolates the property's plumbing and is the valve a householder uses in an emergency. It is normally found where the supply pipe rises into the building, commonly under a kitchen sink, in a utility room or in a downstairs cloakroom.
The external stopcock sits in a chamber at or near the boundary, often under a small cover in a path or verge. It is widely treated as the marker for the change of ownership between the water undertaker's pipe and the property's supply pipe. It is a marker and not the legal test: the Regulations define the supply pipe as so much of the service pipe as is not vested in the undertaker, which is a question of ownership rather than of where a valve was installed.[2]
Role in leak investigation[edit]
The stopcock is the first instrument in most leak investigations even though it is not an instrument at all. Closing the internal stopcock and watching the meter distinguishes a leak inside the property from one on the buried supply pipe outside it: if the meter continues to register with the internal valve closed, the loss is upstream of it.
Stopcocks are also the usual contact points for acoustic listening and for attaching correlator sensors, because they give direct metal-to-metal access to the supply pipe without excavation.
Common faults[edit]
Stopcocks fail from lack of use. A valve that has not been operated for years may seize, or may open but not close fully, and the gland can weep once it is moved. A stopcock that will not shut off completely is a common reason a pressure test cannot be isolated properly and a common cause of an apparent leak that is really a passing valve.
External chambers silt up, are paved over during driveway works, or are lost entirely, which is frequently discovered only when a leak makes the valve necessary.
See also
References
- ^The Water Supply (Water Fittings) Regulations 1999, Schedule 2: requirements for water fittings. legislation.gov.uk. Retrieved 2026-09-05
- ^The Water Supply (Water Fittings) Regulations 1999, regulation 1: interpretation. legislation.gov.uk. Retrieved 2026-09-05