Makes we repair
What to do first when a boiler is leaking water
A boiler leaking water needs the water caught and an engineer called. Vaillant's advice is to turn the heating and the water supply off as well. Water can make the electrical parts in and around a boiler fail, and even start a fire, Vaillant warns. Because of that, act on a leak straight away.
1. Switch the boiler off
Switch the boiler off as its user guide shows. Vaillant's current guide, for one, has you switch it off at its fused spur, the switch on its power supply. Biasi's guides give the same first step for a leak, switching the boiler off and calling an engineer.
2. Catch the water
Put a bucket or another container under the drip, with towels or an absorbent cloth round it. Check the container every so often, so it doesn't overflow.
3. A lot of water: turn it off at the stopcock
The stopcock, the main cold water tap into the home, stops a leak that can't be caught. If the water can't be contained, turn off the stopcock and switch off the electricity to the boiler, as Glow-worm advises. Everyone at home should know where the stopcock is.
4. Leave the casing on, and ring
The inside of a leaking boiler is for a Gas Safe registered engineer to check, Glow-worm says, so don't try to fix it yourself. Never take the casing off, Vaillant says. Ring us and say where the water is.
Sources: Vaillant's page on a leaking boiler and its ecoTEC plus operating instructions, Biasi's Dina and Basica Cond manuals, Glow-worm's page on a leaking boiler, and Ideal's leak FAQ.
Where the water is coming from
Where the water is coming from is the first thing to find. The places to look are a part you can see dripping, damp patches under the boiler, and the pipe outside. Look without taking the casing off.
The makers name these causes:
- pressure that has risen too high, which Vaillant and Glow-worm both call one of the most common
- corrosion
- joints not fully sealed when the boiler was fitted
- worn seals, the pump's included
- a failed heat exchanger, which Vaillant says isn't the most common
The makers don't rank the rest by how often they happen.
Sources: Glow-worm's and Vaillant's pages on a leaking boiler, Vaillant's page on the pressure relief valve and its ecoTEC plus operating instructions, Baxi's page on high boiler pressure and its quick guide, Ideal's leak FAQ, its page on high pressure and its Logic+ Combi2 user guide, and Worcester Bosch's Greenstar 4000 user instructions.
Worth knowing
In a frost, water dripping from a boiler can come from a frozen condensate pipe that has filled and backed up. The white plastic pipe that leaves the house is the one to look at.
What you can safely check
The safe checks for a leaking boiler are the ones the makers' own guides give a householder. Never take the casing off a leaking boiler, and never touch anything that carries gas.
1. Where is it wet?
Look under the boiler, along the pipes below it, and at the radiators and their valves. Look for damp patches on walls or ceilings too. A leak from a radiator or the pipework, not the boiler, still needs catching in the same way.
2. What does the pressure gauge read?
The pressure shows on the boiler's gauge or display. The makers give these readings:
- Baxi: 1 to 2 bar is normal, with the needle in the green.
- Glow-worm: anything above 2 bar, with the heating running and warm, is higher than normal.
- Vaillant: the relief valve opens above about 3 bar.
A reading that keeps falling means water is leaving the system. If the display shows F22 or E119, the boiler has stopped for low pressure. For Vaillant and Glow-worm, the F22 fault code page shows when topping up is safe, and when to stop. For Baxi and Potterton, the E119 fault code page does the same.
3. After a top-up: is the filling loop closed?
The filling loop's valves should both be closed once the pressure is right, and a loop that comes off should be taken off. When the pressure is too high, see that both valves are closed and the loop isn't letting more water in.
4. Pressure too high: bleed a radiator
Bleeding a radiator lets water out of the system and brings the pressure down:
- Switch the heating off and let the radiators cool.
- Hold a cloth under the radiator's bleed valve.
- Open the bleed valve with a radiator key.
- Close the valve when water comes out.
Worcester Bosch's guide stops at 1 to 1.7 bar on the gauge. If the pressure won't stay down, Baxi says to call an engineer.
If the steps in your guide don't stop the water, stop there and ring a Gas Safe registered engineer. We answer calls 24 hours a day.
Sources: Worcester Bosch's Greenstar 4000 user instructions, Viessmann's advice, Ideal's leak FAQ and its page on high pressure, Baxi's page on high boiler pressure, Glow-worm's page on a leaking boiler, and Vaillant's leak and relief valve pages.
When a leak needs an engineer straight away
A leak needs an engineer straight away when any of these is true:
- Water is coming from inside the casing, or from under the boiler.
- Water is on or near the boiler's electrics. Vaillant warns that water can make them fail, or even start a fire.
- The water can't be contained, and you've had to turn it off at the stopcock.
- The pipe on the outside wall drips all the time, or runs.
- The pressure keeps falling, or you keep having to top the system up. A system that needs topping up again and again may have a leak.
- The water is brown, which points to sludge.
- Going on would mean opening the boiler.
If you smell gas as well, don't touch the boiler. The gold "Smell gas?" bar on this page holds the free emergency number. Otherwise, ring us now. A boiler leaking water is on our list of boiler emergencies to ring about straight away.
Ring us too if the boiler is making a new noise as well as leaking. What each boiler noise usually points to. Every other boiler problem, and what each usually means.
Sources: Vaillant's page on a leaking boiler, Worcester Bosch's Greenstar 4000 user instructions, and Glow-worm's page on a leaking boiler.
What changes the price of the fix?
The cost of fixing a leak depends on where the water comes from. A filling loop left open may need no part at all. A seal, a pressure relief valve or an expansion vessel is a part to fit. The rate for the repair is agreed on the call, before anyone comes out, and no work is done until you say yes. How our rates work explains what changes the price.
Do you cover my part of London?
Yes: we fix leaking boilers all over Greater London, day and night, in every borough north and south of the Thames. Pick your side of the river to see the areas.
North of the river
Every borough north of the Thames: Barnet and Enfield at the top, Hillingdon in the west, Havering in the east, and central London in between.
South of the river
Every borough south of the Thames: Richmond and Kingston in the west, Bexley in the east, and down through Croydon to Sutton and Bromley.
Questions about a leaking boiler
Is a leaking boiler dangerous?
Yes, a leaking boiler can be dangerous. Vaillant warns that water can make the electrical parts in and around a boiler fail, or even start a fire. The damp can bring mould too. Switch the boiler off, catch the water and ring us. If you smell gas, open the gold "Smell gas?" bar on this page for the free number.
Can I keep using the boiler?
No, a leaking boiler shouldn't be kept running. Vaillant's advice is to turn the heating and the water off as soon as you see a leak. The law also says a gas appliance you think is unsafe must not be used. When you ring, say where the water is.
Is the pressure falling because of the leak?
A pressure gauge that keeps falling means water is leaving the system, and Viessmann names a leak as the usual cause. Our page on boiler repairs explains what falling or rising pressure usually means.
How much does a leak cost to repair?
A leak's repair cost depends on where the water comes from, and on any part it needs. The rate is agreed on the call before an engineer is sent. How our rates work sets it out.
Don't know what has failed? You don't have to.Ring and say what you can see or hear. Finding the fault is our job.
Calls answered 24 hours a day
A real person answers and gives you the rate on the call. No work starts until you say yes, and repairs are guaranteed for 12 months: parts, labour and any return visit.
