A major water leak can cause serious damage in minutes. Whether it is a burst pipe, water pouring through a ceiling, a leaking cylinder, an overflowing toilet or a hidden pipe failure, the most important thing is to act quickly and safely.

The first steps are simple: stop the water if you can, keep away from electrics, contain the leak, protect your belongings and call a professional if the leak is beyond a simple fix.

This guide explains exactly what to do during a major water leak, what not to do, who may be responsible and when you need emergency help.

Quick answer: what should you do first during a major water leak?

If you have a major water leak, turn off your internal stop tap immediately, switch off electricity at the mains if water is near sockets, lights or appliances, and move people, pets and valuables away from the affected area. Then contain the water with towels, buckets or containers and call an emergency plumber if the leak cannot be safely controlled.

1. Stay calm and check for immediate danger

Before rushing towards the leak, take a few seconds to check the risk.

Do not touch standing water if it is near electrical sockets, lights, appliances, extension leads or your fuse board. Water and electricity are extremely dangerous together.

If water is coming through the ceiling, stay out from underneath the affected area. Ceilings can bulge, crack or collapse if water is collecting above them.

If the leak is near electrics, switch the power off at the mains if it is safe to do so. If you cannot reach the consumer unit safely, leave the area and call for emergency help.

2. Turn off your stop tap

Your internal stop tap controls the mains water supply into your home. Turning it off is usually the fastest way to stop a major leak from getting worse.

The stop tap is commonly found:

• Under the kitchen sink
• In a downstairs toilet
• Under the stairs
• In a utility cupboard
• Near where the mains water pipe enters the property
• In a communal area if you live in a flat

Turn the stop tap clockwise to shut the water off. Then turn on the cold tap in the kitchen to check whether the supply has stopped.

If you live in a flat or shared building and cannot find your own stop tap, contact the building manager, landlord, concierge or neighbours immediately. There may be a communal stop valve.

3. Drain the system

After turning off the stop tap, open the cold taps in your home to help drain water from the pipework. This can reduce the amount of water escaping from the damaged section.

If the leak may involve hot water, a cylinder or heating system, turn off the boiler or heating system as well. Do not touch the boiler, cylinder or controls if water is leaking onto or near electrical components.

4. Switch off electricity if water is near electrics

If water is leaking near sockets, switches, lights, appliances, a consumer unit or wiring, switch off the electricity at the mains if you can do so safely.

Do not unplug wet appliances. Do not touch switches or sockets with wet hands. Do not stand in water while touching electrical equipment.

If there is any doubt, stay clear and call an emergency electrician or the relevant emergency service.

5. Contain the water as much as possible

Once the main water supply is off and the area is safe, try to limit the damage.

Use buckets, bowls, towels or containers to catch water. Move furniture, rugs, electronics and valuables away from the affected area. If water is coming through the ceiling, place a bucket underneath the drip and protect the floor with towels.

If there is a visible small split or leak in a pipe and the water has slowed down after turning off the stop tap, you may be able to wrap the pipe temporarily with a towel, cloth or plumber’s tape while waiting for professional help. This is only a temporary measure and should not be treated as a repair.

6. Identify where the leak is coming from

Once the emergency is under control, try to work out the likely source.

Common causes of major water leaks include:

• Burst pipes
• Failed pipe joints
• Leaking toilets
• Overflowing baths, basins or sinks
• Faulty washing machine or dishwasher hoses
• Leaking hot water cylinders
• Boiler or heating system leaks
• Damaged pipework under floors or behind walls
• External supply pipe leaks
• Drainage issues causing wastewater to back up

If the leak is clean water and stops when the stop tap is turned off, it is likely related to your water supply pipework.

If the water continues even after the stop tap is off, it could be from stored water, a heating system, a tank, a cylinder, an appliance or a neighbouring property.

If dirty water or sewage is backing up through a toilet, bath, shower or drain, this is a drainage emergency rather than a clean water leak.

7. Check your water meter if the leak is hidden

If you suspect a hidden leak but cannot see where it is coming from, your water meter may help.

Turn off all taps and appliances that use water. Wait for a short period so toilets and tanks are not still filling. Then check whether your water meter dial or numbers are still moving. If they are moving while no water is being used, this can indicate a leak.

You can also turn off your internal stop tap and check the meter again. If the meter is still moving after the internal stop tap is off, the leak may be between the meter and your property. If it stops moving, the leak is more likely inside the home.

8. Call an emergency plumber or drainage specialist

Call a professional straight away if:

• You cannot stop the water
• The leak is affecting electrics
• Water is coming through a ceiling
• You cannot find your stop tap
• The leak is from a cylinder, boiler or heating system
• The leak is inside a wall, floor or ceiling
• Wastewater or sewage is backing up
• More than one fixture is affected
• You live in a flat and the leak may affect other properties
• The leak has caused visible property damage

A professional can isolate the issue, carry out a safe repair and check whether further damage or drainage problems are involved.

9. Contact your water company if the leak may be outside

Not every leak inside or around a property is handled in the same way.

As a general rule, leaks inside your home or on your private supply pipe are usually your responsibility. Public water mains and many leaks under roads or pavements are usually handled by the water company.

If you see water bubbling up outside, running along the pavement, pooling in the road or coming from a public area, report it to your water company.

If the leak is between your water meter and your home, responsibility can depend on the property boundary and pipe layout. If you are not sure, contact your water company and ask for guidance.

10. Take photos and contact your insurer

If the leak has caused property damage, take clear photos and videos before moving or throwing anything away. Capture the source of the leak if visible, damaged flooring, walls, ceilings, furniture and any standing water.

Then contact your home insurance provider as soon as possible. They may advise you on emergency repairs, drying equipment, approved contractors and what evidence they need for a claim.

Keep receipts for emergency callouts, temporary repairs, replacement items and drying equipment.

11. Dry the affected area properly

After the leak is repaired, the area needs to dry properly. Wipe up standing water, ventilate the room, use dehumidifiers if available and remove soaked items where safe.

Do not ignore damp patches, bubbling paint, warped flooring or musty smells. These can be signs of trapped moisture.

If the leak has affected ceilings, walls, insulation or flooring, professional drying or damage assessment may be needed.

12. Prevent future major leaks

Once the immediate issue is resolved, take steps to reduce the chance of it happening again.

Make sure everyone in the property knows where the stop tap is. Test the stop tap occasionally so it does not seize. Replace old appliance hoses. Insulate exposed pipework in cold areas. Fix small leaks quickly. Watch for damp patches, water stains, low pressure, unusual sounds and unexplained increases in water usage.

A small warning sign can become a major leak if it is ignored.

What not to do during a major water leak

Do not touch electrics if water is nearby.

Do not ignore water coming through a ceiling.

Do not keep using taps, toilets, showers or appliances until the issue is understood.

Do not assume the leak has stopped just because visible water has slowed down.

Do not remove damaged materials before taking photos if you may need to claim on insurance.

Do not attempt pipe repairs if you are unsure what you are doing.

Do not pour chemicals down drains if the problem involves wastewater backing up.

When is a water leak an emergency?

A water leak is an emergency if it is uncontrolled, close to electrics, damaging ceilings or walls, affecting multiple rooms, causing flooding, involving wastewater or making the property unsafe.

It is also an emergency if you cannot find or turn off the stop tap.

Final thoughts

The most important steps during a major water leak are to act quickly, stay safe and stop the water at the source if possible. Turn off the stop tap, avoid electrics, contain the water, protect your belongings and call a professional if the leak cannot be safely controlled.

Once the leak is repaired, document the damage, speak to your insurer and make sure the affected area is dried properly. Fast action can make the difference between a manageable repair and serious property damage.

FAQs

What is the first thing to do when you have a major water leak?

Turn off your internal stop tap if it is safe to do so. Then avoid electrics, contain the water and call an emergency plumber if the leak is serious.

Where is my stop tap usually located?

It is often under the kitchen sink, under the stairs, in a downstairs toilet, in a utility cupboard or near where the mains water pipe enters the property.

Should I turn off electricity during a water leak?

Yes, if water is near sockets, switches, appliances, lights or your fuse board. Only switch it off if you can reach the mains safely.

Who is responsible for a water leak outside my home?

Leaks inside your home or on your property are usually your responsibility. Leaks on public pipes, roads or pavements are usually handled by the water company. If you are unsure, report it and ask your water supplier.

Can I repair a major water leak myself?

You may be able to contain the leak temporarily, but major leaks should usually be repaired by a qualified plumber. Incorrect repairs can cause more damage.

What should I do if water is coming through the ceiling?

Stay out from directly underneath it, turn off the water supply, switch off electricity if safe, place a bucket under the leak and call an emergency plumber.

Should I call my insurance company after a leak?

Yes, if the leak has caused damage to walls, ceilings, floors, furniture or belongings. Take photos and videos before clearing too much away.