Stopcock Leaking: Causes, Quick Checks and Repair Options
Water weeping from your stopcock, around the spindle or from the joints either side? Why stopcocks leak, what you can safely check yourself and when repair or replacement is the better fix.
A stopcock usually leaks from one of two places: around the spindle under the handle, where the gland packing has worn, or from the compression nuts where the valve joins the pipe. A slow weep from the spindle can often be stopped by nipping up the gland nut a fraction of a turn. A leak from the joints, a valve that is corroded, or one that leaks more when you turn it usually means the stopcock should be replaced. Put a bowl underneath and keep the area dry until it is fixed.
Key Takeaways
- Work out where the water is coming from before doing anything: spindle, body or joints.
- A spindle weep is often the gland packing and can sometimes be fixed with a small turn of the gland nut.
- Leaks from the joints or a cracked, corroded body need a proper repair or a new stopcock.
- Replacing the main stopcock means isolating the supply outside, which is not always possible in flats.
- Old stopcocks that leak when turned are also the ones most likely to fail in an emergency.
A leaking stopcock is usually either weeping from the spindle under the handle, because the gland packing inside has worn, or leaking from the nuts where the valve joins the pipe. A gentle spindle weep can often be stopped by tightening the gland nut a fraction of a turn. A leak from the joints, a badly corroded body, or a valve that drips every time you turn it is normally a sign the stopcock needs replacing. Until it is fixed, put a container underneath, keep the cupboard dry and avoid turning the valve more than you have to.
Where is the stopcock leaking from?
Dry the valve and the pipe either side with kitchen roll, then watch for a minute to see where the first bead of water appears. Water runs down pipes and drips from the lowest point, so the wet patch is rarely where the leak starts.
| Where the water appears | Likely cause | Typical fix |
|---|---|---|
| Around the spindle, just under the handle | Worn or dried-out gland packing | Tighten the gland nut slightly, or repack the gland |
| Only when you turn the handle | Packing no longer seals as the spindle moves | Repack or replace the valve |
| From the nut where the pipe enters | Loose, damaged or corroded compression joint | Remake the joint, often with new olive |
| From the valve body itself | Corrosion, dezincification or a crack | Replace the stopcock |
| From the pipe below the valve | Pipe leak rather than a valve leak | Pipe repair, possibly on the supply pipe |
Look at the colour of the valve too. Old brass stopcocks that have turned pink or white and crusty on the outside are often suffering from dezincification, where the zinc leaches out of the brass and leaves it porous and weak. Those valves tend to weep from the body and are not worth repairing.
How urgent is a leaking stopcock?
A slow drip that you can catch in a bowl is not an emergency, but it should be dealt with soon for two reasons. First, even a small leak inside a kitchen unit can rot the base, swell chipboard and cause mould without you noticing. Second, the stopcock is your main way of turning the water off in an emergency. If it already leaks, there is a real chance it will leak much worse, or fail to shut, on the day a pipe bursts.
Treat it as urgent if water is spraying rather than dripping, if the leak is getting faster, if water is reaching electrics or flooring, or if you are in a flat where a leak could reach the property below. In that case, find the outside stop valve if you can, turn the supply off there, and call a plumber.
What you can safely check
If the water is coming from around the spindle, you can try tightening the gland nut. It is the small hexagonal nut directly under the handle, around the spindle, and it squeezes the packing that stops water escaping along the spindle.
Support the valve body
Hold the body of the stopcock with one spanner or grips so the pipe does not take any twisting force.
Tighten the gland nut gently
Turn it clockwise by no more than a quarter turn with a second spanner.
Dry it and wait
Wipe it dry and check again after ten minutes. If it has stopped, leave it alone.
Stop if it gets worse
If the leak continues after a small turn, or the handle becomes very stiff, stop and book a repair.
Do not try to tighten the compression nuts on the pipes if the valve is old and corroded. Copper pipe that has been in place for decades can be thin, and a slipping spanner can split the joint. If the leak is from those nuts, the joint usually needs remaking with the water off. If the stopcock is stiff as well as leaking, our guide to a stopcock that won't turn explains what not to force.
Repair or replace?
Repacking a gland or remaking a joint can be a good repair on a sound valve. In practice, most leaking stopcocks we see in London are the original fitting in a house or flat that is decades old, and replacing it is the better long-term fix. A new valve is not expensive as a part, and the labour is similar to a repair because the water has to be isolated either way.
Replacement usually makes sense when:
- The valve body is corroded, crusty or weeping.
- It leaks every time you turn it.
- It does not fully shut the water off.
- It is so stiff that you have to force it.
The main stopcock cannot be swapped without first turning off the water before it. That usually means the outside stop valve in the pavement or front garden. If that valve is missing, buried or seized, a plumber may use a pipe freezing kit to form a temporary ice plug, or you may need to contact the water company about the valve on their side. It is worth checking whether you can find and lift the outside cover before the visit, because it affects how the job is planned. Our stopcock location page shows the usual places to look.
If the leak turns out to be on the pipe itself rather than the valve, particularly an old lead supply pipe, you may be looking at a water leak repair rather than a simple valve swap. Our plumbing labour is £95 an hour, and the plumber will confirm what the job involves and the price before starting.
Leaking stopcocks in London flats
In a flat the stopcock may be in a kitchen cupboard, the bathroom, a hallway cupboard or a communal riser, and the outside stop valve may serve the whole building. That changes things in two ways. A leak can quickly become a problem for the flat below, and turning off the supply to replace your stopcock may cut off neighbours too. Speak to your managing agent or freeholder about isolation before the work is booked, and if you rent, report the leak to your landlord in writing.
Thames Water's guidance is that pipes on your property are your responsibility, while public water pipes are theirs. The internal stopcock inside your flat is almost always yours or your landlord's to maintain. Shared supply pipes can be less straightforward, so keep a note of who you have spoken to and when.
Leaking stopcock you don't trust any more?
Tell us where the water is coming from and whether you can reach an outside stop valve. We'll arrange a plumber and confirm the price before any work starts.
📞 Call 020 7870 3200More on our stopcock repair and replacement service.
If the leak has already caused damage, or water has got into a ceiling below, our guide to what to do after a burst pipe covers the next steps and the records worth keeping for insurance.
Frequently Asked Questions
Is a leaking stopcock an emergency?
A slow drip that a bowl can catch is not usually an emergency, but it should be fixed within days. It becomes urgent if water is spraying, soaking into floors or reaching electrics, or if the valve leaks badly when you try to turn it, because you may not be able to isolate the water when you need to.
Why does my stopcock leak when I turn it?
Turning the handle moves the spindle through the gland packing. On old valves that packing has dried out or worn, so it seals while the valve sits still but lets water past once the spindle moves. Nipping up the gland nut can help, but a valve that leaks every time it is used is usually due for replacement.
Can I tighten a leaking stopcock myself?
You can try tightening the gland nut, the small nut directly under the handle, by a quarter turn or less using a spanner while supporting the valve body. Do not overtighten it, and do not tighten the compression nuts on the pipe while the valve is under strain, because old pipe and fittings can crack.
Who is responsible for a leaking stopcock?
The internal stopcock inside your home is the homeowner's responsibility, as is the supply pipe from your boundary into the house. The outside stop valve in the pavement and the public pipes are normally the water company's. In rented homes, report it to your landlord or agent.
Do I need to turn the water off outside to replace a stopcock?
Yes. Replacing the main stopcock means isolating the supply before it, usually at the outside stop valve near the boundary. If that valve cannot be found or operated, the plumber may need to use a pipe freezing kit or arrange isolation with the water company.
Sources and further reading
Source links checked 27 September 2026. Scheme rules and manufacturer instructions can change; use the current official guidance for your account or exact appliance.