What to Do in a Plumbing Emergency in London: The First Hour, in Order

The first sixty seconds

There is a correct order, and it is not the order most people follow. The instinct is to find the leak. The right move is to remove the pressure driving it, because a located leak at full mains pressure is still doing damage while you look at it, and an isolated leak is not.

Three actions, in this order. Turn the water off at the nearest valve that covers the failure. Look up and decide whether electricity is involved. Move people, and anything that matters, out from underneath. Everything else, including photographs, insurers and phone calls, comes after those three.

The three valves worth knowing before you need them

Almost every London property has more than one point of isolation, and knowing which does what saves minutes that matter.

• The internal stop tap. Shuts the cold mains to the whole property. Usually under the kitchen sink, in a hall or airing cupboard, under the stairs, or behind a bath panel. In converted flats it is sometimes in a communal riser cupboard on the landing.
• The external stop valve. A small cast iron cover in the footpath or front path, needing a key. It is the water company's asset, it may serve more than one property, and it is the fallback when the internal tap has seized.
• Service valves. Small isolating valves on individual runs, turned with a flat screwdriver, typically at the toilet, under basins, on the cylinder feed and at the boiler. These let you kill one appliance without taking the whole property off.

If the internal tap is stiff, do not fight it. A seized stop tap that snaps off in your hand turns a contained leak into an uncontrolled one, and there is a proper way to deal with a leaking or seized stopcock that does not involve a pair of pliers at midnight.

Once the mains is off, open the lowest cold tap in the property and let the system drain down. Pipework holds a considerable standing volume, and draining it is what actually stops the flow rather than merely slowing it.

Decide whether it is safe before you do anything else

Water and electricity together is the part of a plumbing emergency that hurts people, and it is the part that gets least attention because the water is more visible.

If water is running near a consumer unit, dripping from a light fitting, tracking down a wall containing sockets, or standing on a floor with cabling in it, isolate the affected circuits at the consumer unit before you go near them. If the consumer unit itself is wet, do not touch it at all: leave the property, and call an electrician or, if there is any sign of arcing or burning, the emergency services. No plumbing repair is worth that risk.

A ceiling holding water is a structural problem, not a plumbing one

A plasterboard or lath and plaster ceiling that has taken on water will bow, then sag, then come down, often as one piece. People are injured standing underneath with a bucket, which is exactly where the instinct puts them.

Clear the room below, keep everyone out, and if the ceiling is visibly bulging, treat it as unsafe until an engineer has seen it. Piercing a bulge to drain it in a controlled way is sometimes the right call, but it is a judgement about which way the water and the ceiling will go, and it needs to be made by somebody standing to the side with the electrics already off. Our guide to water leaking through a ceiling covers that assessment in detail.

Contain the water, then record everything

With the pressure off and the area safe, the next few minutes are about limiting damage and preserving evidence. Both matter, and they are easy to do at the same time.

• Get containers under any continuing drip, and lift soft furnishings, rugs and anything electrical clear of standing water.
• Open windows and get air moving. Trapped humidity is what turns a wet week into a mould problem.
• Photograph and film before you mop. Wide shots for extent, close shots for source. Once a room is dried, there is nothing left to show anybody.
• Note the time you discovered it, not the time you called someone.
• If you are metered and can safely reach the meter, read it with everything closed. A meter still turning is direct evidence that water is still escaping somewhere on your side.
• Keep anything that failed. A split length of pipe or a burst flexible hose is physical proof the failure was sudden, and it is worth more to a claim than any description.

That last point is the one people regret. The single most common reason an escape of water claim is reduced is the gradual damage exclusion, and the evidence that defeats it is usually the part that got thrown in the skip.

Who to call, and in what order

Not every plumbing emergency belongs to the same person, and calling the wrong one first is the commonest way to lose an hour.

What is happening	First call	Why
Water escaping inside your own home	Emergency plumber or leak detection engineer	Yours to stop and yours to repair, then notify the insurer
Water bubbling up in the street or footpath	Your water company	Their main or their communication pipe, and they will attend to it
Wet patch on your drive or garden, meter still turning	Leak detection	Supply pipe after the boundary is the property owner's responsibility
Any smell of gas	National Gas Emergency Service, 0800 111 999	Free, 24 hours. Ventilate and leave before you call
Water coming from the flat above	The neighbour, then the managing agent	Access to the source is the only thing that stops it
You rent the property	Landlord or letting agent, on their emergency number	Repairs to the water and sanitation installations are the landlord's duty
Sewage backing up into the property	Water company or your drainage contractor	Depends which side of the boundary the blockage sits
Wet ceiling with any sign of electrical involvement	Isolate the circuit, then an electrician	The hazard is electrical before it is plumbing

If you rent, the landlord's repairing obligations for water and sanitation installations are statutory under section 11 of the Landlord and Tenant Act 1985, and they cannot be contracted away by a clause in a tenancy agreement. Report the emergency in writing as well as by phone, because the record of when you told them is what establishes liability for the damage that follows. In social housing, Awaab's Law sets specific timescales for emergency hazards, and Citizens Advice publishes clear guidance on both.

Leaks outside your boundary belong to somebody else

Ofwat sets out the split for households: the main in the road and the communication pipe up to the property boundary are the water company's, while the supply pipe from the boundary into the building is the owner's. Water surfacing in the street is a call to Thames Water, Affinity Water or whichever company serves your postcode. A wet patch on your own drive with the meter still turning is yours, and if you are metered the company's leakage allowance scheme may credit some of the water lost once the repair is done.

What a competent emergency visit actually does

An emergency attendance is not the same job as a repair booking, and the sequence a good engineer follows is deliberately front-loaded towards making the situation stable before anything gets opened up.

Stage	What should happen	What it prevents
Make safe	Confirm isolation, check for electrical involvement, assess ceilings and floors	Injury, and a second incident while the first is being fixed
Establish the system	Identify whether it is mains, stored cold, hot, heating or waste	Chasing the wrong circuit for an hour
Confirm the loss	Meter check, pressure check, isolate sections and observe	Opening up a wall for a leak that is not there
Locate	Acoustic, thermal, moisture mapping or tracer gas as the case requires	Exploratory damage charged as investigation
Record	Photographs, readings and a written account of what was found and eliminated	A claim that rests on your description alone
Repair or make secure	Permanent repair where possible, a controlled temporary one where not	Leaving the property without a working supply
Hand over	What was done, what remains, and what to watch	The same engineer being called back to a different symptom

Two things in that sequence are worth insisting on. The first is that nothing gets cut into before the loss has been confirmed and located, because a speculative hole is damage you pay for twice. The second is the written record. Most buildings policies pay for finding a leak under the trace and access section, and that payment is made against a report, not against a recollection.

Why locating comes before opening up

Water travels. It runs along joists, down the back of a stud, inside a conduit and across a screed before it appears, and the point where it shows is frequently metres from the point where it left the pipe. That is the entire reason non-invasive emergency leak detection exists: to convert a wet ceiling into a marked point, so that the single hole made is the right one.

The common emergencies and what each one needs

The symptoms differ enough that the immediate action differs too.

Symptom	Do this first	What it usually is
Water spraying or pouring, visible source	Stop tap off, drain the lowest tap	Burst pipe, failed flexible hose, split fitting
Ceiling stain spreading while you watch	Clear the room, isolate the circuits below	A leak in the floor above, often a bath or shower waste
Boiler pressure falling repeatedly	Stop topping it up, note the rate of loss	Heating circuit leak, or a failed expansion vessel
Meter turning with every tap closed	Isolate at the stop tap and re-read	Supply pipe leak, or a passing toilet or valve
Warm or damp patch on a floor	Turn the heating off and keep the area clear	Underfloor heating or a buried heating flow
Water in a basement or lift pit	Isolate power to the area, then pump	Supply pipe, groundwater, or a failed drainage pump
Foul smell with slow drainage	Stop running water into the system	Blocked drain rather than a leak
No water at all, neighbours affected too	Check the water company's outage page before calling anyone	A mains issue, not your property

A burst is the one case where speed genuinely changes the outcome, because the volume involved is large from the first second. The specific sequence for that case, including what to do about the electricity and the heating, is set out in what to do first with a burst pipe.

What changes in a London flat

A converted terrace or a purpose built block introduces two problems a house does not have: the water may not be yours, and the valve may not be reachable.

If water is coming from above, the only thing that stops it is somebody isolating the supply in that flat. Knock first. If there is no answer, call the managing agent or freeholder's emergency line, which is obliged to be contactable, and keep a record of the time of every call. Communal risers and the pipework within them are usually the freeholder's responsibility rather than any individual leaseholder's, and so is the block's buildings insurance. Your contents are yours.

There is also a legal boundary worth understanding before anyone starts apportioning blame. Broadly, a leaseholder is responsible for the pipework within their demise, the freeholder for common parts, and liability for damaged belongings turns on negligence rather than simply on which flat the water came from. Citizens Advice and the Leasehold Advisory Service both publish guidance on this, and it is worth reading before an argument starts rather than during one.

The practical difficulty in a block is proving where the water actually originated when two leaseholders disagree. That is an evidence problem, and it is solved with moisture mapping and a documented survey rather than with assertion. It is also the reason we write reports for managing agents and property managers in a form that stands up when it is passed to an insurer or a loss adjuster.

The things that make it worse

Most of the avoidable cost in a plumbing emergency comes from a short list of mistakes.

• Searching for the leak before isolating. Every minute spent looking is a minute of water at full pressure.
• Restoring the supply to test a repair too early. Bring the pressure up slowly and watch, rather than opening the stop tap fully and walking away.
• Cutting into a ceiling from directly underneath. Stand to the side, with the circuits off.
• Repeatedly topping up a heating system. Each top-up adds fresh oxygenated water and hides the rate of loss, which is the single most useful diagnostic you have.
• Mopping and drying before photographing. The insurer sees a tidy room and a claim with nothing behind it.
• Stripping out wet material before notifying. Mitigation is required of you. A full strip-out before the insurer has seen the scope is not mitigation.
• Assuming the damp patch is above the leak. It very often is not, and cutting where it shows is how a small repair becomes three holes.

If the water is stopped, the property is safe and nothing is actively getting worse, you have converted an emergency into a booking, and you can take the time to choose who attends rather than accepting whoever answers. If it is not stopped, that is what 24 hour emergency cover across London is for, and the call is better made early than late.