Stopcock Leaking

What's happening?

A stopcock leaks in three places, and WaterSafe describes each. Water around the joints is usually loose or worn nuts and seals. Water rising from the spindle, under the handle, points at the gland nut and its packing. A valve that turns but still lets water pass has a washer or internal part that needs replacing. A slow leak at a stop tap is easy to ignore, but it wets the floor and wall around it and, more importantly, a valve that leaks is often the one you cannot trust to shut off in an emergency. If it will not turn at all, see the stopcock won't turn page.

What usually causes it?

• Gland packing around the spindle dried out or worn
• A loose gland nut that has not compressed the packing
• A loose or worn compression nut at a pipe joint
• A perished washer so water seeps past when shut
• A cracked valve body from frost, corrosion or past force
• Mineral build-up on the spindle damaging the packing every time it moves

Is it dangerous?

Medium. A leak at the main stop tap often means the valve can no longer be trusted to shut off. Water running down a wall can reach electrics or damage plaster and flooring. Do not turn it hard to test it if the body looks cracked or corroded.

Can I fix it myself?

Isolate the water first if you can, and open a cold tap to drain the pipes. WaterSafe describes the simple fixes: a weeping compression nut can take a quarter turn while you hold the tap body steady, and if it still weeps, undo the nut, wrap PTFE tape around the threads and refit. Water at the spindle may stop with a slight nip on the small gland nut; if not, lift the gland nut, add PTFE tape around the spindle and retighten. After any repair turn the water on slowly, check every joint and look again after 24 hours. Avoid forcing seized parts, and do not work on a valve you cannot isolate.

When should you call a plumber?

Call a plumber when the valve body is cracked or corroded, when a quarter turn does not stop the leak, when the valve does not shut off, when the stop tap is the only isolation and the leak worsens, or when it feeds a shared supply.

What will the plumber actually do?

• Isolate the supply, from a servicing valve or the external stop tap where permitted, and drain down
• Re-pack the gland, remake the compression joint or replace the washer
• Replace the stop tap, and fit a servicing valve beside it where none exists
• Check the pipe either side and the pipe clips for movement that caused the wear
• Refill slowly and test all joints, then recheck for seepage

Who fixes this

• Stopcock replacement
• Leak repair

What it usually costs

Stopcock Replacement Cost

£100–£200

Leaking Pipe Repair Cost

£100–£500 for an emergency burst pipe

Questions people ask

Sources & References

1. WaterSafe: what to do if your internal stop tap is leaking or broken
2. HomeServe: how to fix a leaking stopcock
3. The Water Supply (Water Fittings) Regulations 1999, Schedule 2 (watertight fittings)