Leaking Stopcock: How to Fix It
Reviewed by the Devon Leak Detection team. Last updated June 2026
The short answer
Most leaking stopcocks drip from the gland nut around the spindle. Turn off the water first, then gently tighten the gland nut with a spanner. If it still weeps, re-pack the gland with PTFE tape. A leak from the body usually means the valve needs replacing.
A stopcock that drips, weeps or trickles is one of the most common little plumbing problems in a Devon home, and it is rarely as serious as it first looks. The stopcock (or stop tap) is the valve that controls the mains water coming into your property. When it starts leaking, the water usually appears around the handle or at one of the pipe joints, and a small towel underneath buys you time while you work out what is going on.
The good news is that many stopcock leaks are a quick fix with a spanner and a bit of PTFE tape. The key is knowing exactly where the water is escaping, because the fix is different for each spot. Below we walk through the three places a stopcock leaks, how to deal with each one, and when it is wiser to call a plumber rather than keep tweaking it.
Turn off the water before you touch anything
If you are going to undo the gland nut or work on the valve, you need the water off first. The internal stopcock you are trying to fix is the one valve you cannot rely on, so isolate the supply upstream of it. In most Devon homes the next valve along is the external stop tap, usually found near the boundary or pavement under a small cover roughly the size of a CD case.
A word of caution here. The external stop tap belongs to your water supplier, not to you. You may need permission to operate it, and some suppliers ask you to contact them first. Turn it clockwise, slowly and never with force. Many of these taps sit deep in the ground and need a stop tap key, which you can buy cheaply from a plumbers’ merchant. If you cannot reach it or it will not budge, that is a sensible point to call a professional rather than risk damaging it.
Once the water is off, open a cold tap at the lowest point in the house to drain the pipe and release the pressure. Now you can work on the stopcock without a soaking.
Where is the stopcock actually leaking from?
Before reaching for tools, dry the whole valve with a cloth and watch where the water reappears. A stopcock leaks from one of three places, and pinning it down saves you taking apart the wrong part.
The three places to check:
- The gland nut around the spindle, just below the handle. This is the most common spot, and you often see it drip only when the valve is open.
- The compression nuts on either side, where the valve joins the pipework. Water here points to a loose or tired joint.
- The body of the valve itself. A leak through the brass body, or one that will not stop after the above, usually means the stopcock is worn out.
Fixing a leak at the gland nut
The gland nut sits directly under the handle and squeezes a soft packing material against the spindle to form a watertight seal. Over the years that packing dries out and the seal goes, so water creeps up the spindle and out around the nut.
The first thing to try is the simplest. With a spanner, give the gland nut a gentle quarter turn clockwise to compress the existing packing a little more. Go carefully. Over-tighten it and the spindle becomes stiff and hard to turn. For a tired but not failed seal, this small nudge is often all it takes.
If it still weeps, the packing needs replacing. With the water off, hold the headgear nut steady with one spanner and undo the gland nut anti-clockwise with another. Slide the gland nut up the spindle, then pick out the old packing with a small screwdriver or a penknife. Wrap several turns of PTFE tape tightly around the spindle in a clockwise direction, push it down into the gland, slide the nut back over it and tighten gently. Turn the stopcock fully open, then back a half turn so it does not seize, and check for drips as the water comes back on.
Fixing a leak at the compression nuts
A stopcock has a compression nut on each side, joining it to the incoming and outgoing pipes. If the water is appearing at one of these joints rather than around the spindle, the fix is usually straightforward. Hold the valve body still and nip the offending nut up a little with a spanner, no more than a gentle eighth to quarter turn at a time, checking between each adjustment.
If the joint keeps weeping after a careful tighten, the olive (the small ring inside the joint) may have deformed or corroded. Renewing an olive means draining the pipe and remaking the joint, which is fiddly on a mains stopcock and easy to make worse. If a light tighten does not settle it, this is a good moment to bring in a plumber rather than keep cranking the nut.
When the stopcock needs replacing
Some stopcocks are simply past saving. If the brass body is cracked or weeping through itself, if the handle is seized solid, or if the nut threads are rounded off, no amount of tightening or re-packing will hold for long. Re-packing the gland with PTFE will stop a spindle leak, but on a valve that is used often it can wear through again before too long, so a worn valve is usually best swapped out.
Replacing a mains stopcock means cutting it out and fitting a new one, and it relies on the upstream supply being shut off cleanly first. For many homeowners that is a job worth handing to a qualified plumber who can fit approved parts. Look for someone on the WaterSafe register, who can advise on whether yours can be repaired or is better replaced.
When the leak is not the stopcock at all
Sometimes the water pooling near the stopcock has actually travelled there from somewhere else. Water runs downhill and along pipes, so a damp patch under the kitchen sink, in the cupboard, or near where the mains enters the house can be misleading. If you have dried, tightened and re-packed the valve and water keeps returning, the source may be a joint or pipe behind the wall or under the floor.
A useful early check is your water meter. Turn off every tap and appliance, then watch the meter for a few minutes. If it is still ticking over, water is escaping somewhere on your supply even when nothing should be running. That is a sign of a hidden leak rather than a simple stopcock drip, and it is exactly the kind of problem we trace without ripping up floors. Our water leak detection uses non-invasive methods to pinpoint where the water is really coming from across Devon, so any repair work is focused on the right spot.
For more practical guidance on plumbing problems around the home, browse our other articles.
Frequently Asked Questions
If you are only nipping up the gland nut by a small amount you may manage without, but it is safer to isolate the supply first. To re-pack the gland or work on a joint, the water must be off. Use the external stop tap upstream, then open a low tap to drain the pipe before you start.
That is the gland nut, which seals the spindle as it passes through the valve. The soft packing inside dries out over time and lets water creep up. A gentle quarter turn on the gland nut often stops it; if not, the packing needs replacing with fresh PTFE tape wrapped around the spindle.
The external stop tap belongs to your water supplier, so you may need their permission to operate it, and some ask you to contact them first. Turn it slowly and never force it. If it is stuck or buried deep and you cannot reach it safely, it is best to leave it to a professional.
A spindle or joint leak can often be repaired with a tighten or fresh packing. If the body is cracked, the handle is seized, or the threads are rounded, replacement is usually the better choice. A qualified plumber can fit approved parts and advise on which makes sense for your valve.
If you have tightened and re-packed the valve and water keeps appearing, the real source may be elsewhere. Check your water meter with everything turned off; if it keeps ticking, you likely have a hidden leak on the supply that needs tracing rather than another stopcock repair.
Not sure the stopcock is the real problem?
If the water keeps coming back, we can trace exactly where it is escaping across Devon, no digging guesswork.