A leaking stopcock that weeps when closed is usually not urgent. Most drips come from the gland nut around the spindle, and a gentle quarter turn on that nut often stops it. It becomes urgent when water is flowing rather than dripping, when the valve will not shut the supply off, or when water is near electrics.
You turned the stopcock off, perhaps to change a tap washer or because you were heading away for a few days, and noticed a bead of water forming under the handle. Or there is a small damp ring on the cupboard floor that was not there last week. It is unsettling because this is the one valve that is supposed to stop water, and here it is letting some through. In almost every case the news is better than it looks. This guide explains where a stopcock leaks from, how to tell a tired seal from a failing valve, the one small adjustment worth trying, and what your backup is if the valve itself is the problem.
Is it urgent? The quick test
Two things decide this: how fast the water is moving, and whether the valve still does its job.
- A slow weep you can catch in a bowl. Water beading around the spindle or a nut, a few drops an hour. Not urgent. A job for this week.
- A steady drip that has not changed in days. Still a routine job, but put a container under it and keep an eye on the level so you know if it is getting worse.
- Water flowing, spraying or spreading across the floor. Urgent. Shut the supply off at the outside stop valve if you can and get a plumber out promptly.
- The stopcock will not turn, or turns but water still runs at the taps. Urgent, because you have no way to isolate the house. Use the outside valve and arrange a replacement soon.
- Water reaching sockets, a fuse board or the back of an appliance. Urgent regardless of the rate. Isolate the electrics at the consumer unit if it is safe to reach, then the water.
If you are firmly in the first two groups, you have time. A weep will not fix itself, and a weep today is often a drip in a month, but it is not a flood in the making.
Where the water is coming from
Dry the whole valve with a cloth, then watch where the water reappears. A stopcock leaks from one of four places and each has a different meaning.
The gland nut
This is the nut directly under the handle, around the spindle. Inside it is a ring of soft packing that seals against the spindle as it turns. Over years of sitting untouched the packing dries and shrinks, and water creeps up the spindle and out under the nut. This is by far the most common stopcock leak, and it often shows only when the valve has just been operated, which is why you noticed it after turning the water off.
The compression nuts
These are the two larger nuts either side of the valve where it joins the pipe. A drip here means the joint has worked slightly loose or the olive inside has tired. It is usually the easiest leak to cure with a careful nip up, but the fitting can be damaged by overtightening, so go gently.
The headgear joint
The joint where the upper section of the valve screws into the body. A leak here after the valve has been operated can be a tired washer or a joint that needs remaking. It is fixable but needs the water off upstream.
The body
Water seeping through the brass casting itself, or a leak that carries on no matter what you tighten, means the valve is worn out or cracked. Old stopcocks in Cornish cottages and farmhouses can be seventy years old and were never designed to last that long. A body leak is the one that needs a replacement rather than an adjustment.
| What you notice | Most likely cause | What to do |
|---|---|---|
| Weep under the handle, worse just after turning | Gland packing worn | Quarter turn on the gland nut, then re-pack if needed |
| Drip at a large nut beside the pipe | Compression joint loose | Gentle tighten, replace olive if it persists |
| Drip from the joint below the handle assembly | Headgear washer or joint | Water off upstream, plumber to remake |
| Water through the brass, or leak will not stop | Valve body failed | Replace the stopcock |
| Valve closed but taps still run | Jumper or washer failed inside | Replace, and use the outside valve meanwhile |
The quarter-turn trick
For a gland weep there is a simple first step that needs one spanner and no water off. Put the spanner on the gland nut, the small one right under the handle, and turn it a quarter turn clockwise. That compresses the packing a little more against the spindle. Stop there. If the spindle becomes stiff you have gone too far, and forcing an old valve is how handles snap. For packing that is tired rather than finished, a quarter turn is often all it takes and the weep stops within minutes.
If it still weeps after a second small nudge, the packing needs replacing. With the water off upstream, hold the headgear nut still with one spanner and undo the gland nut anticlockwise with another. Lift the nut up the spindle, pick out the old packing, wrap several turns of PTFE tape clockwise around the spindle, push it down into the gland, and refit the nut gently. Open the valve fully, then close it a half turn so it does not seize in the open position. That last habit is worth adopting on any stopcock.
One caution. A stopcock that has not moved in years may not take kindly to being turned at all. If it feels solid, do not force it with a longer lever. Penetrating oil and patience, or a plumber, are the safer routes.
When to call someone
Call a plumber rather than keep tweaking when the leak is from the body or the headgear, when the valve will not close the supply, when the compression nut still drips after a gentle tighten, or when the valve is so old that a new one is the sensible answer anyway. A replacement stopcock is a routine plumbing job.
Call a leak detection specialist when the stopcock is not really the story. A damp cupboard floor is sometimes blamed on the visible valve when the water is actually coming from the supply pipe where it rises through the floor, or from a joint hidden behind the cupboard back. If you tighten everything, the valve is dry, and the floor is still wet, that is a hidden leak, and a water leak detection survey locates it without taking the kitchen apart. The same applies if your water meter is turning with everything off. Our guide on a water meter moving when nothing is on explains that test.
Your backup: the outside stop valve
Almost every property has a second shut-off point near the boundary, usually under a small plastic or metal cover in the pavement, drive or front garden, often in the same chamber as the water meter. In Cornwall this valve up to the boundary belongs to South West Water, and the supply pipe from there into the house belongs to you. You can operate it in an emergency, and if you cannot reach it or it will not move, South West Water can isolate the supply for you.
To use it, lift the cover, and if the tap is deep in the chamber use a stop tap key, which any plumbers’ merchant sells cheaply. Turn it clockwise, slowly and without force. Then open a cold tap indoors at the lowest point to drain the pipe and take the pressure off the leaking stopcock while you work on it or wait for the plumber. Long rural supply pipes, common on farms and houses outside villages around Wadebridge and Launceston, can take a while to drain, so give it a few minutes.
Find this valve now, while it is dry and daylight. If you have never found your inside stopcock either, where the stopcock hides in older Cornish houses covers the usual places.
Insurance and responsibility
The internal stopcock and everything after it is the property owner’s to maintain. A drip from a worn gland is wear and tear, which insurance does not pay to fix. Damage caused by a sudden failure, such as a cracked body that floods a kitchen, is usually covered as an escape of water under a buildings policy, and many policies include trace and access cover for locating a hidden leak. If you rent, section 11 of the Landlord and Tenant Act 1985 puts the installations for the supply of water on the landlord, so report a leaking stopcock in writing and let them arrange the repair.
We provide leak detection across Cornwall, and when the drip turns out to be the visible end of a hidden leak, the report we leave marks the repair point for your plumber and sets out the cause for your insurer.
Frequently asked questions
Why does my stopcock only leak when it is closed?
Turning the valve moves the spindle through the gland packing, and worn packing lets a little water past as it moves or when the position changes. Closing the valve also puts full mains pressure on the seal inside. A gentle quarter turn on the gland nut usually stops a weep that appears after operating it.
Is a leaking stopcock an emergency?
Rarely. A slow weep from a nut or the spindle can wait a day or two for a plumber. It is urgent if water is flowing rather than dripping, if the valve will not shut the supply off, or if water is reaching electrics. In those cases use the outside stop valve and call a plumber promptly.
Can I tighten a leaking stopcock myself?
Yes, carefully. A quarter turn clockwise on the gland nut under the handle often stops a spindle weep, and a gentle nip on a compression nut can stop a joint drip. Never force a stiff old valve. If tightening does not stop it, the packing or the valve needs replacing.
Who is responsible for the stopcock, me or South West Water?
The stopcock inside your home and the supply pipe from the boundary are yours. South West Water is responsible for the communication pipe and the meter up to the boundary stop valve. You may operate the outside valve in an emergency, and they can isolate the supply if it will not move.
Should I replace an old stopcock that weeps?
If the gland trick fails or the valve is very old, stiff or leaking from the body, replacement is the sensible answer. Modern lever valves are easier to operate in a hurry. Ask the plumber to fit it somewhere you can reach quickly, and turn it a couple of times a year so it does not seize.
Dry valve, wet floor?
If you have tightened everything and the cupboard floor is still damp, the leak is probably not the stopcock. We locate hidden leaks on supply pipes across Cornwall without taking kitchens apart, and leave you an insurance-ready report.
