Radiator Leaking? How to Stop the Drip and When to Call Us

A radiator leaking water is usually coming from one of four places: the valve at either end, the nut joining the valve to the radiator, the little bleed valve at the top, or a pinhole in the radiator itself. Most of the time you can stop the drip yourself in a few minutes by closing both valves, which buys you time to get it repaired properly. If you’re in Clare, Sudbury, Long Melford, Haverhill or a village nearby, here’s what to do, and where to stop.

Radiator leaking? Work out where the water is coming from

Let the heating cool first, then dry the radiator and pipes with a towel and wrap a piece of dry kitchen roll around each joint. The one that gets wet first is your leak. Water runs along pipes, so a puddle under one end doesn’t always mean that end is the culprit.

• Round the valve spindle (under the head or cap): a worn valve gland, common on older valves and often worse when the heating is on.
• At the nut where the valve meets the radiator, or where the pipe goes into the valve: a joint that has worked loose or a perished seal.
• From the bleed valve at the top corner: the bleed screw is slightly open or its seat is worn.
• From the body of the radiator, often along the bottom: a pinhole caused by corrosion from inside. Brown or black water is a clue. A radiator in this state needs replacing, not patching.

Step by step: how to stop a leaking radiator

1. Turn the heating off and let the radiator cool. Radiator water can be hot enough to scald, so give it time before you handle the valves.
2. Keep water away from electrics. If drips are reaching a socket, extension lead or anything plugged in, don’t touch them. Switch off at the consumer unit (fuse box) only if you can stand somewhere completely dry.
3. Catch the water. Put a bowl or baking tray under the drip and lay old towels down. Carpets and floorboards soak water up fast, and a leak upstairs can show through the ceiling below.
4. Close the thermostatic or wheel-head valve. Turn it clockwise as far as it will go by hand. On a thermostatic radiator valve (TRV), that’s the 0 or off setting, not the snowflake, which is frost protection and still lets water through.
5. Close the valve at the other end. This is usually the lockshield valve, with a plastic cap that pulls or unscrews off. Underneath is a small brass spindle you can turn clockwise with an adjustable spanner. Count the turns as you go and write the number down. That valve sets how much hot water the radiator gets, and the number lets an engineer set it back afterwards. If it won’t move with gentle pressure, leave it.
6. If the bleed valve is dripping, gently close it clockwise with your radiator key. Don’t overtighten it.
7. Check your boiler pressure. On most modern sealed systems there’s a gauge on or under the boiler, normally around 1 to 1.5 bar when cold. A leak lets pressure fall, and the boiler may lock out. You can top it up through the filling loop, but only exactly as your boiler’s user manual describes. Worcester Bosch’s boiler pressure guide shows the common types. Older homes with a tank in the loft don’t have this gauge.
8. Take a photo or two of the valve, the joint and any label on the radiator. It helps us bring the right parts first time.

With both valves closed, the rest of your heating can usually be used as normal while you wait for the repair. If the drip carries on with both valves shut, the leak is on the pipework side and the water has to be stopped further back, so call us.

Avoid these mistakes

• Don’t undo the nuts, take a valve off or try to drain the radiator. Once a valve is open to the system, water can pour out much faster than you can catch it.
• Don’t use a sealant, tape or an off-the-shelf “leak sealer” added to the system unless an engineer has recommended it. Some can block valves and the boiler’s heat exchanger.
• Don’t keep topping up the boiler pressure to keep the heating going. If the pressure keeps falling, the leak needs fixing and the boiler needs looking at by a Gas Safe registered engineer.
• Don’t take the boiler casing off or touch anything inside it. Your boiler actions are limited to what the user manual allows: checking the power, timer and thermostat, the reset button and topping up the pressure.
• Don’t reset a tripped RCD or breaker more than once. If it trips again, leave it off and call a registered (Part P) electrician.

When to stop and call us

• The leak carries on even with both radiator valves closed.
• A valve is seized, spins without shutting, or is weeping from the spindle.
• Water is coming from the body of the radiator, or the water is brown or black. Our radiator repair team can replace the radiator or valves, and if sludge is the cause, a power flush may be worth talking about.
• Your boiler keeps losing pressure or keeps locking out. That’s a job for our Gas Safe engineers through our boiler repair service.
• Water has gone through a ceiling or into flooring and you can’t tell how far. Our leak detection service can trace it.
• The water won’t stop. Turn off your inside stopcock (see how to find and turn off your stopcock), read what to do with a flood or burst pipe, and call our emergency plumbing team.

The outside or boundary stop tap is usually owned by your water company (Anglian Water or Essex & Suffolk Water) and may need a special key, so don’t dig it up or force it. If you think there’s a leak on their side, check whether neighbours are affected and contact the water company.

Smell gas or suspect carbon monoxide? Leave the property, open doors and windows if it’s safe, don’t use light switches or naked flames, turn the gas off at the meter only if it’s safe to do so, and call the National Gas Emergency Service on 0800 111 999. Get medical advice if anyone has CO symptoms such as headaches, dizziness or nausea. Only a Gas Safe registered engineer may work on gas appliances; you can check an engineer on the Gas Safe Register.

Sources and further reading

• Which? Trusted Traders: how to stop a water leak
• Worcester Bosch: what to do if your boiler loses pressure
• Worcester Bosch: how to bleed a radiator
• Your boiler manufacturer’s user manual, for the correct pressure and how to use your filling loop.

This is general safety guidance. If you’re unsure, stop and call a qualified engineer.