A leaking stopcock is usually not an emergency. A slow weep from a nut or the spindle can often wait a day or two for a plumber. It becomes urgent when water is flowing fast, when the stopcock won't turn off so you can't isolate the supply, or when water is near electrics. In those cases, shut off the water and call a plumber straight away.
Spotting water around your stopcock is unsettling, but it rarely means a flood is coming. Most stopcock leaks are slow drips from a worn nut or seal. Annoying and worth fixing, but not a 2am crisis. What matters is how fast the water is moving and whether you can still turn the supply off. This guide covers when a leaking stopcock is genuinely an emergency, what to do first, the simple fixes you can try yourself, and when to call in a professional.
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Is a leaking stopcock an emergency? The quick test
Most of the time, a leaking stopcock is a job for the week, not the night. The deciding factor is the rate of water and whether you can still isolate the supply. Here is the simple split.
| Treat as an emergency if… | Usually NOT an emergency if… |
|---|---|
| ✘ Water is flowing or spraying, not just dripping | ✔ A slow drip or weep you can catch in a bowl |
| ✘ The stopcock won't turn off, so you can't isolate the supply | ✔ The stopcock still turns and shuts the water off |
| ✘ Water is reaching sockets, fuse board or appliances | ✔ The damp is contained to the immediate area |
| ✘ Water is pooling and spreading across the floor | ✔ A small weep from a nut that hasn't changed in days |
If anything in the left column applies, turn the water off and get a plumber out promptly. If you're firmly in the right column, you have time to try a simple fix or book a routine visit. Either way, a leak won't fix itself. A weep today is often a steady drip in a few weeks.
What a stopcock is and why it leaks
Your internal stopcock (or stop tap) is the valve that turns off the cold water supply to your whole home. It's usually under the kitchen sink, or where the mains pipe first enters the property, sometimes in a downstairs cupboard, utility room or garage. Turning it clockwise shuts the water off, and that's your first move in almost any plumbing emergency.
Stopcocks leak because they're mechanical parts that wear. Most are made of brass and contain rubber washers and a packed gland that keep water from escaping around the moving spindle. Over years of sitting untouched, those seals harden, the washer perishes, and the joints can loosen. A stopcock that's rarely turned is also more likely to seize. That's why the simplest maintenance, turning it off and on a couple of times a year, genuinely helps.
Where is your stopcock leaking from?
Pinning down the exact spot tells you how serious it is and whether it's a quick fix. There are four common leak points.
The compression nuts
These are the nuts that join the stopcock to the pipe on either side. A drip here is often just a nut that has worked slightly loose, and it's usually the easiest leak to cure.
The gland nut
This sits just below the handle, around the spindle. If water appears from the top of the stopcock when you turn it, or weeps around the spindle, the gland packing inside has likely worn. It's a common leak and usually fixable without turning the water off.
The head-gear joint and body
The head-gear joint is where the upper section screws into the main body. A leak from the body itself, or from a crack in the brass, is the most serious. Old, corroded stopcocks can fail here, and that often means replacing the whole valve rather than repairing it.
What to do right now
- Judge the flow. Is it a drip you can catch, or water that's running? That decides whether this is urgent.
- Contain the water. Put a bowl and towels under the leak to protect the floor and units while you decide your next step.
- Try to isolate the supply if it's serious. If water is flowing fast, turn the stopcock off. If it won't budge, don't force it (see below). Go to your outside stop tap instead.
- Keep water away from electrics. If the leak is anywhere near sockets or the consumer unit, treat it as an emergency and call a professional.
- Photograph it. If there's any water damage, take pictures before you clean up, in case you need to claim on insurance.
If the stopcock won't turn off
A seized internal stopcock is common in older homes, and forcing it is the worst thing you can do. Old brass can snap, turning a drip into a burst. WaterSafe advises against forcing seized parts and recommends an approved plumber instead. Your fallback is the outside stop tap, usually under a small cover near your boundary or the pavement. Knowing where it is before you need it is well worth a couple of minutes, and our guide on how to find the shut-off valve for water shows you where to look.
Who's responsible, you or the water company?
This trips a lot of homeowners up. The split is straightforward: the internal stopcock inside your home is your responsibility, so you arrange and pay for the repair. According to Ofwat, the water company is responsible for the pipework up to the property boundary or the outside stop tap. Everything beyond that point, including your internal stopcock and supply pipe, sits with you as the homeowner.
So if the leak is on your internal stopcock, it's your job to sort. If it's the external stop tap out by the boundary, or clearly on the public side, contact your water supplier. In our area that's South West Water. The Consumer Council for Water notes that some suppliers offer help locating and repairing supply-pipe leaks, so it's always worth asking before you pay for work yourself.
DIY fixes you can safely try
For a minor leak, a confident DIYer can often sort a stopcock with basic tools: an adjustable spanner, a screwdriver and some PTFE tape. The fix depends on where it's leaking.
A drip from a compression nut
Try gently tightening the nut a small amount with a spanner. Often that's all it takes. Don't crank it hard, as over-tightening can damage an old fitting or distort the pipe.
A weep from the gland nut
First, tighten the gland nut a little, being careful not to over-tighten to the point where the handle won't turn. If it still weeps, the packing inside has worn and needs replacing: unscrew the gland nut and slide it up the spindle, pick out the old packing, wrap a few turns of PTFE tape around the spindle, then slide the nut back down and re-tighten. As HomeServe notes, you don't usually need to turn the water off for this. Just keep a tray underneath for the small flow.
When to stop and call a plumber
Leave it to a professional if the body is cracked or corroded, the valve is seized, the leak is getting worse, or you simply have any doubt. Both WaterSafe and HomeServe make the same point: don't force fragile pipework, and call a plumber the moment you're unsure. A failed DIY attempt on an old stopcock can turn a small job into a flooded kitchen.
When to call a professional, and when it's a leak specialist
Most leaking-stopcock repairs are a job for a local plumber, and that's the right call for a worn washer, a seized valve or a stopcock that needs replacing. A professional plumbing leak detection approach comes into its own when the water around your stopcock isn't obviously coming from the stopcock at all. Think damp with no clear source, a hissing pipe, or a water bill that's crept up without an explanation. A bill that has climbed for no obvious reason sometimes traces back to something as simple as a constantly running toilet, so it is worth ruling that out too.
That's where non-invasive detection finds the true source before anything is opened up, using thermal imaging, acoustic listening and tracer gas. Escape-of-water damage is the most common and costly home insurance issue going, with UK insurers paying out around £1.8 million a day for it, according to the Association of British Insurers. Finding a hidden leak early really does save money and disruption.
Frequently asked questions
Is a leaking stopcock an emergency?
Usually not. A slow weep from the spindle or a nut can often wait a day or two for a plumber. It becomes an emergency when water is flowing fast, when the stopcock won't turn off so you can't isolate the supply, or when water is reaching electrics. In those cases, turn off the water and call a plumber straight away.
Who is responsible for fixing a leaking internal stopcock?
The internal stopcock inside your home is the homeowner's responsibility, so you arrange and pay for the repair. The water company is responsible up to the boundary or the outside stop tap. If the leak is on the external stop tap or the public side, contact your water supplier.
Can I fix a leaking stopcock myself?
Often, yes, for a minor leak. A drip from a compression nut can be eased by tightening it gently, and a weep from the gland nut can usually be cured by tightening it or re-packing it with PTFE tape. If the body is cracked, the valve is seized, or you have any doubt, call a plumber rather than forcing it.
What should I do if my stopcock won't turn off?
Don't force a seized stopcock, as you can snap it and make the leak far worse. Instead, turn off the water at your outside stop tap, usually under a small cover near the boundary or pavement, and call a plumber. Knowing where your outside stop tap is before you need it is well worth a few minutes.
Will home insurance cover a leaking stopcock?
Insurance rarely pays to repair the stopcock itself, as that's usually treated as maintenance. It may, however, cover water damage caused by a sudden leak under the escape-of-water part of a buildings policy. Check your policy schedule, and keep photos and invoices if you need to claim.
How do I stop a leaking stopcock making the leak worse?
Put a bowl and towels under the drip to protect the floor, and avoid over-tightening, which can crack an old brass body. If the leak is getting worse, isolate the supply at the outside stop tap. For anything beyond a minor weep, a plumber is the safer route than repeated DIY attempts.
Damp around your stopcock with no clear source?
If the water isn't obviously the stopcock, or a bill has crept up without explanation, we trace hidden leaks across Cornwall & Devon with non-invasive equipment, so we find it before anything's opened up. Fast response, minimal damage.
Call Dickie on 07822 025 911 No Find, No Fee on residential leak detection (subject to terms)