A stop tap, often called a stopcock, is the main valve that isolates the cold water supply to a property for maintenance, alteration or emergencies such as burst pipes. UK installations typically include a stop tap on the rising main inside the property, often near the kitchen sink, and an external boundary stop tap owned by the water supplier, which in Greater London is usually Thames Water. UK valves are manufactured to BS 1010 and must be accessible at all times under the Water Supply (Water Fittings) Regulations 1999. Homeowners should know the location of their internal stop tap and test it periodically by closing and reopening it gently. Stuck or seized stop taps are a common problem in older London properties and may require replacement by a qualified plumber.
Stop tap (stopcock)
Main valve isolating the cold water supply to a property for maintenance or emergencies.
