What Is an Internal Stop Tap (Stopcock) and What Does It Control?

Key takeaways

• An internal stop tap (also called a stopcock/stop valve) is the valve that shuts off the water supply to your home or business. (watersafe.org.uk)
• Guidance describes it as the point where the water supply to the property can be shut off. (watersafe.org.uk)
• Turning the incoming stopcock off can turn off all the water supply to the property. (southampton.gov.uk)
• In an emergency, knowing where it is (and that it works) matters, because you may need to stop the incoming mains water quickly. (watersafe.org.uk)

What is an internal stop tap (stopcock), and what does it control?

An internal stop tap (stopcock) is a valve used to shut off the water supply to a home or business. It controls the incoming water supply into the property, so you can stop the water when needed (for example, during a leak or plumbing work). (watersafe.org.uk)

Put simply: it’s the main “off switch” for the property’s water supply.

What parts of the water supply does it shut off?

Guidance describes the internal stop tap/stopcock as the point where the water supply to the home or business can be shut off. (watersafe.org.uk)

A council housing guide is even more direct: turning the incoming stopcock off “will turn off all the water supply to your property.” (southampton.gov.uk)

That means it’s the valve you use when you need to stop water reaching the property’s pipework.

How does this relate to shutting off the incoming mains supply in an emergency?

In an emergency (such as a burst pipe or major leak), the internal stop tap is typically the quickest way to stop water flowing into the property—because it’s designed to shut off the supply at the point it enters your home/business. (watersafe.org.uk)

WaterSafe also advises being aware of the location of your internal stop tap because you may need it in an emergency. (watersafe.org.uk)

Where is the internal stop tap usually found?

Locations vary by property, but WaterSafe notes that in a home it’s usually under the kitchen sink, and it can also be in an airing cupboard or under the floorboards near the front door. (watersafe.org.uk)

Southampton City Council’s guidance also notes the incoming stopcock is normally found in places like the kitchen, bathroom, and sometimes the airing cupboard. (southampton.gov.uk)

Common mistakes to avoid

• Not knowing where it is until there’s a problem. WaterSafe recommends knowing its location in case of an emergency. (watersafe.org.uk)
• Forcing a stiff valve. Southampton City Council advises not to force a stopcock that is stiff or hard to turn. (southampton.gov.uk)

Quick summary

An internal stop tap/stopcock is the valve that shuts off the water supply to your property—the point where you can stop the incoming supply, including in an emergency. Turning off the incoming stopcock can turn off all water to the property, so it’s worth knowing where it is and ensuring it can be operated safely. (watersafe.org.uk)