Is a leaking stopcock an emergency?

A slow weep from the spindle is not an emergency, but it should be dealt with soon. A steady drip from the body or a joint, or any leak you cannot slow, is urgent, because the stopcock is the valve you rely on to stop every other leak in the house.

Why did my stopcock start leaking after I turned it?

Turning a stopcock that has not moved in years disturbs the packing around the spindle, and water weeps out past it. A gentle quarter turn of the gland nut just under the handle often stops it. If not, the packing needs renewing or the valve replacing.

Can I replace a stopcock myself?

It needs the water isolated at the outside stop tap or communal valve, the pipe cut and new joints made, and the job tested under mains pressure. Some confident DIYers do it, but if the outside tap is hard to reach or the pipework is lead or old iron, it is a job for a plumber.

How do I turn off the water if my stopcock is leaking?

Use the outside stop tap, usually under a cover in the pavement or front garden near the boundary, which normally needs a long key. In a flat, the supply may be controlled from a communal riser or plant room. Contain the leak with a container and towels while you arrange it.

Will the water company fix a leaking stopcock?

Not the one inside your property. Water companies are generally responsible for the outside stop tap and the pipe in the street. The internal stopcock and the supply pipe on your side of the boundary are the owner of the property to repair.

Should I leave a stiff stopcock alone?

Not indefinitely. A stopcock that is too stiff to turn is not doing its job. Turn it gently, and if it will not move without force, get it replaced rather than forcing it, which can snap the spindle or crack the body.

Stopcock Leaking? What to Do Now and When to Replace It

Most leaking stopcocks leak from one of three places: around the spindle where the handle goes in, which is the gland and can often be stopped with a gentle quarter turn of the gland nut; from the compression joints either side, where the pipe goes in; or from a crack in the body itself. A drip from the spindle, especially just after the valve has been turned for the first time in years, is common and usually minor. A leak from the body, or one you cannot slow, needs the water turned off further back at the outside stop tap and the stopcock replaced. Put a container and a towel under it now, then work out which of the three you have.

Find exactly where it is leaking from

Dry the whole valve with a cloth or kitchen roll, then watch where the first bead of water appears. It sounds fussy, but water runs along pipes and drips from the lowest point, which is often not where it is coming out.

From around the spindle, just under the handle: the gland packing has worn or dried out. This is the commonest leak and usually the easiest to deal with.
From the nut where a pipe enters the valve: a compression joint has loosened or the olive inside it has failed.
From the body of the valve itself, often a hairline line or a green or white crust: the casting has cracked or corroded. This needs replacing.
From the pipe below or above, not the valve: the stopcock is innocent and the leak is on the pipe, which is a different repair.

Leaking from the spindle after you turned it

Stopcocks often go years without being touched. The packing around the spindle dries and settles in place, and the first time someone turns the handle, it disturbs that packing and water weeps out around the spindle. People often notice it the day after a plumber has isolated the water, or after testing the stopcock themselves.

Just under the handle is a small nut, the gland nut. With a spanner, tighten it by a quarter turn, gently, and see if the weeping stops. Do not force it: too much and the handle becomes stiff, and on an old brass valve the spindle can snap. If a quarter turn slows it but does not stop it, another small nudge is reasonable. If it makes no difference, the packing needs renewing or the valve replacing.

Turning the stopcock fully open and then back a fraction can also help, because on some valves the back seat of the spindle seals the gland when fully open. This is worth trying before reaching for a spanner.

Leaking from a joint or from the body

A compression joint that has started weeping can sometimes be stopped by nipping up the nut slightly. Hold the valve body steady with a second spanner while you do, because twisting the valve on the pipe can make a small leak much worse. If the joint was made years ago and the olive has corroded, tightening will not seal it and the joint needs remaking.

A crack in the body is not something to tighten or seal. Brass and gunmetal castings do crack, particularly after a frost or after years of dezincification in older brass, and a crack can open further without warning. The valve needs replacing, and the water needs turning off before that can happen.

Do not wrap a cracked stopcock in tape or filler and leave it. It is the valve that stops everything else in the house, so a failing one is not a leak you want to rely on when something else goes wrong.

How to turn the water off when the stopcock is the leak

This is the awkward part. The stopcock is normally how you turn the water off, but you cannot fully rely on a valve that is itself leaking, and replacing it means isolating the supply further back.

That further point is the outside stop tap, usually under a small metal or plastic cover in the pavement or front garden near the property boundary. It belongs to the water company and generally needs a long key to reach. In a block of flats, the supply to your flat may be controlled from a communal riser, a meter cupboard or a basement plant room, often by the building manager. Knowing where yours is before you need it saves a great deal of stress, and our guide on where your stopcock is and how to use it covers the places to look.

While you arrange that, keep the leak contained. Turn the stopcock as far off as it will safely go if that slows it, put a container underneath, and move anything valuable or electrical away from the area.

Repair or replace?

A worn gland on a sound valve can be repacked, and a failed joint can be remade. Both are small jobs. Replacement is the better choice when the body is cracked or badly corroded, when the valve will not close fully so it cannot do its job in an emergency, or when it is so seized that turning it is likely to cause a leak.

Many older London properties still have the original stopcock under the kitchen sink or in a cupboard under the stairs, and some are on lead or old iron pipe where the joint to the valve is the weak point. Replacing an old stopcock with a modern quarter turn valve or a new stopcock is a routine job, and it is worth doing before the day you need to shut the water off in a hurry.

Who is responsible for a leaking stopcock?

The internal stopcock and the pipe from the property boundary into the house are the owner of the property to look after. The outside stop tap and the pipe in the street are the water company. In rented homes, the landlord is responsible for the internal stopcock, and in leasehold flats it depends on what your lease says about pipes serving only your flat. Our guide to who is responsible for a leak in a leasehold flat covers the detail.

Getting it fixed

If the gland nut has not stopped it, the leak is from the body, or you cannot turn the stopcock off at all, call us or send an enquiry with a photo of the valve and where it sits. We have 20 engineers across London, and a stopcock replacement is usually done in a single visit once the supply is isolated. Our rate is set out on the pricing page and agreed before we attend. If water is already coming through a ceiling or reaching electrics, treat it as an emergency and our guide on water escaping explains what to do first.

Questions we get asked

Is a leaking stopcock an emergency?: A slow weep from the spindle is not an emergency, but it should be dealt with soon. A steady drip from the body or a joint, or any leak you cannot slow, is urgent, because the stopcock is the valve you rely on to stop every other leak in the house.
Why did my stopcock start leaking after I turned it?: Turning a stopcock that has not moved in years disturbs the packing around the spindle, and water weeps out past it. A gentle quarter turn of the gland nut just under the handle often stops it. If not, the packing needs renewing or the valve replacing.
Can I replace a stopcock myself?: It needs the water isolated at the outside stop tap or communal valve, the pipe cut and new joints made, and the job tested under mains pressure. Some confident DIYers do it, but if the outside tap is hard to reach or the pipework is lead or old iron, it is a job for a plumber.
How do I turn off the water if my stopcock is leaking?: Use the outside stop tap, usually under a cover in the pavement or front garden near the boundary, which normally needs a long key. In a flat, the supply may be controlled from a communal riser or plant room. Contain the leak with a container and towels while you arrange it.
Will the water company fix a leaking stopcock?: Not the one inside your property. Water companies are generally responsible for the outside stop tap and the pipe in the street. The internal stopcock and the supply pipe on your side of the boundary are the owner of the property to repair.
Should I leave a stiff stopcock alone?: Not indefinitely. A stopcock that is too stiff to turn is not doing its job. Turn it gently, and if it will not move without force, get it replaced rather than forcing it, which can snap the spindle or crack the body.