Water in: supply, leaks and frozen pipes

Water comes into a house under pressure, through one pipe, and most of what goes wrong with it happens where nobody looks: under a lawn, in a crawl space (the low space under a raised ground floor), inside a toilet, in a pipe along an outside wall on the coldest night of the year. This lesson follows the water from the street to the taps. You'll learn who is responsible for which length of pipe, how to tell whether your pressure is normal, how to prove a leak exists before you hunt for it and how much a drip really wastes, and what to do on the morning a pipe freezes, which is where the UK and US advice part company.

Nothing in this lesson opens a pipe, so the callout's "isolate the water" matters here mainly on the morning a pipe freezes. Then it means the stop tap (stopcock) in a UK home, or the main shut-off valve in a US one, which you found in lesson 1, How a house works, and where it switches off. WaterSafe's rule for turning it is short: "Turn it on and off slowly, never force it."[7]

Whose pipe is it?

Before anyone pays to fix a leak, find out whose leak it is. In England and Wales the answer comes from the Consumer Council for Water (CCW), the consumer body for water there, and it splits the pipe at your property boundary.¹

The water main in the street is owned by the water company. CCW says the company is also responsible for the pipe that joins the main to your boundary, for "The external stop tap usually located in the public footpath", and for the water meter, if you have one.¹ From the boundary inwards the pipe is the homeowner's responsibility: "The homeowner is responsible for maintaining any water pipes located on private property up to the boundary of the road where the company’s water main is laid."¹ If one pipe serves several properties, CCW says it becomes the joint responsibility of all the owners connected to it, and a leak in the pipes and fittings inside the house is the homeowner's to have repaired.¹

This is general information, not legal advice. The rules differ between England, Wales, Scotland and Northern Ireland, and between US states and cities, and they change. CCW's split is for England and Wales. This course did not research who is responsible for which pipe in Scotland or Northern Ireland, and in the US it varies by utility, which the course did not research either, so there your water company or utility is the one to ask. The rule behind the split comes from an official consumer body describing responsibility in England and Wales. The job that follows from it, a leak on the homeowner's side of the boundary, is Call someone: a plumber, and CCW says it's the homeowner's responsibility to arrange the repair.¹ CCW's page is written to homeowners. If you rent, the person to tell is your landlord or whoever owns the home; this course didn't research what a tenancy says about who arranges it.

Is your pressure normal?

Weak flow is the other complaint that sends people looking for a plumber, and WaterSafe, the register of approved plumbers run for the UK water industry, gives a test you can do at the sink.² With every other tap and appliance turned off, the first tap in the house, usually the kitchen tap, "should be able to fill a 4.5 litre (one gallon) bucket in 30 seconds".² That comes to 9 litres a minute, by this course's arithmetic. WaterSafe offers it only as a guide, and only for a home with a suitable single service pipe, so a slow bucket on its own does not prove the company is at fault. WaterSafe doesn't define a single service pipe. This course reads it as a supply pipe that serves your home alone, not one shared with the neighbours.

The figures behind the guide belong to the companies. Pressure is measured where the company's pipe meets yours, "usually the outside stop valve or property boundary", and WaterSafe says: "Most water companies will aim to provide at least 10 metres head (approximately 14 psi or 1.0 bar) at the end of their communication pipes. They are committed to a guaranteed standard of service to provide a minimum of 7 metres static head (0.7 bar)."² That is WaterSafe's account, and it doesn't say which nations it describes.

In England and Wales, the 7 metres is law. The Water Supply and Sewerage Services (Customer Service Standards) Regulations 2008 set it for each country separately. For England, regulation 17G says: "An English water wholesaler must maintain, in a communication pipe serving premises supplied with water, a minimum water pressure of seven metres static head". For Wales, regulation 10 puts the same duty on "A Welsh water undertaker".[11] The wholesaler and the undertaker are the regulations' names for the water company that runs the mains. A communication pipe, in the regulations' definition, is "the part of a service pipe between an English wholesaler’s water main and the boundary of the street in which the water main is laid" (the Welsh definition is the same, and both have a variant for a house that fronts straight onto the street).[11] In other words, the standard is measured on the company's side of the boundary, not at your tap. If the pressure there falls below 7 metres for an hour or more, and does so again within 28 days, other than during necessary works or a drought, the regulations give the customer a payment: £50 in England, up to £250 in a financial year, and £25 in Wales, once in a financial year. There are further exceptions in the text.[11] This is general information, not legal advice. This course didn't research Scotland or Northern Ireland.

"Metres head" sounds odd until you see how WaterSafe explains it in plain words. It says water companies are required to supply water at a pressure that will reach the top storey of most homes, with some exceptions, and it describes the guide flow as enough to fill a cold-water cistern in the roof space of a two-storey house.² WaterSafe does not define "head". This course's reading of those two examples is that head is pressure described as a height the water can be pushed to. Ten metres is about 1 bar or 14 psi (pounds per square inch), in WaterSafe's own conversion; a bar is a unit of pressure, and 0.7 bar is about 10 psi, which is this course's conversion.

In the US this course read no national pressure figure and no home test from an official source. Your utility is the place to ask.

A slow bucket in a shared house

A converted Edwardian house in Hampshire has been split into three flats. The owner of the top flat times her kitchen tap into a 4.5 litre bucket with everything else in the flat turned off. It takes 55 seconds, nearly twice WaterSafe's 30.

The first question is whether WaterSafe's guide applies at all. It is written for a home with a suitable single service pipe, and three flats in one old house may well share a pipe from the street. She doesn't know, and a bucket can't tell her. Nor can her tap show what the company supplies, because WaterSafe says pressure is measured at the outside stop valve or boundary, and she is two floors up and at the far end of the house's own pipes.²

So the bucket has done its job: it says something is worth asking about. WaterSafe points readers to their water company for more information,² and that is her next step. The two questions she takes to it are her own: is the supply to the house shared, and what is the pressure at the boundary? If it turns out the flats share one pipe and that pipe needs work, CCW's account (general information, not legal advice) makes it the joint responsibility of all the owners connected to it.¹ The bucket test is Yours. Any work on a shared supply pipe is Call someone, and a conversation with the neighbours first.

How much a drip wastes

People leave drips alone because a drip looks like nothing. The numbers say otherwise, and they come from different places measuring different things, so read each one with its label.

The figures, each with its source and what it counts:

• One tap, United States: "A leaky faucet that drips at the rate of one drip per second can waste more than 3,000 gallons per year" (EPA WaterSense, "Fix a Leak Week").³ "Faucet" is the American word for a tap.
• One tap, England: Southern Water, an English water company, says a slow drip can waste "up to 10,000 litres per year".⁵ It does not define "slow", and "up to" makes it a ceiling, not an average.
• Whole households, United States: "The average household's leaks can account for more than 9,300 gallons of water wasted every year and nine percent of homes have leaks that waste 50 gallons or more per day" (EPA, "Fix a Leak Week").³ EPA's own "Statistics and Facts" page gives 9,400 gallons for the same average, so call it more than 9,000 US gallons.⁴ Worn toilet flappers and dripping faucets are among the common household leaks EPA names. A flapper, in EPA's description, is the rubber part that holds water in a US toilet tank and lets it into the bowl when you flush.³
• Toilets, one English water company's customers: United Utilities says "Nearly 80% of all leaks reported to us last year were leaky loos!" and that a faulty cistern can cost "as much as £400 a year" in wasted water.[6] That is a share of the leaks its own customers reported, not of all leaks. The page does not say which year "last year" was, and £400 is a ceiling.

One trap for anyone who reads both countries' advice: a US gallon is not a UK gallon. EPA's gallons are US gallons of about 3.8 litres (this course's conversion). WaterSafe's "4.5 litre (one gallon)" bucket[2] is an imperial gallon, by this course's reading. Convert through litres and the two countries' figures sit side by side: EPA's one-drip-a-second tap wastes more than 11,000 litres a year, and Southern Water's slow drip up to 10,000. They are different measures from different organisations, and they land in the same range.

Drips scale simply. A tap that drips once every two seconds rather than every second wastes about half EPA's figure, a little over 1,500 US gallons or about 5,700 litres a year. That is this course's arithmetic, and it assumes drips of the size EPA's figure implies. To turn water into money, use the price per cubic metre (UK) or per thousand gallons (US) on your own bill, if you're metered. Fixing the drip itself is the next lesson, lesson 3, Taps and toilets.

Proving a leak before you hunt for it

A leak you can see is easy. The expensive ones are those you can't, and EPA gives two tests that find them without opening anything.³

The meter test. Read your water meter "before and after a two-hour period when no water is being used. If the meter changes at all, you probably have a leak."³ Two hours with no water means nobody flushes, runs a tap, or starts the dishwasher or the washing machine. The test needs a meter, so it is no use in an unmetered home. United Utilities adds a UK wrinkle for its own customers: if your meter is outside the house and you have checked inside and found nothing, the leak may be on your outside supply pipe.[6] In England and Wales that is the pipe CCW puts on the homeowner's side of the boundary.¹

The dye test. Put a few drops of food colouring in the toilet tank (the cistern, in UK terms) and don't flush. "If any color shows up in the bowl after 10 minutes, you have a leak."³ EPA suggests flushing straight afterwards so the tank does not stain.³ EPA wrote the test for American toilets. Using it on a UK cistern is this course's own step, and the reasoning is only this: the test asks whether water gets from the cistern into the bowl without a flush, and that question is the same whatever is inside the cistern.

EPA also gives a rough check on the bill. For a family of four, if water use in a colder month such as January or February goes above 12,000 US gallons, there could be serious leaks.³

Both tests are Yours. They are EPA's advice to householders, they change nothing, and they suit any home.

Frozen pipes

Why a frozen pipe splits. The American Red Cross gives the mechanism in a line: water "expands as it freezes", and "No matter the strength of a container, expanding water can cause pipes to break."[10] The Met Office adds the part people miss: pipes freezing and then thawing can cause them to burst, so the danger is not over when the ice melts.[8]

The pipes most at risk, in the Red Cross's list for US homes, are outdoor hose bibs (outside taps), pipes in unheated basements, crawl spaces, attics, garages and kitchen cabinets, and pipes against outside walls with little or no insulation.[10]

Keeping them from freezing

This is advice, and each country's comes from its own bodies.

In the UK, CCW's winter advice is to find your stop tap, lag exposed pipes (wrap them in insulation), fit covers on outside taps, put insulating jackets on tanks, cisterns and boilers, fix dripping taps, and keep a registered plumber's number handy.[9] The Met Office says: "Make sure you know where your stop tap is and check it’s working every six months." It also says to leave the heating on low if you go away, and to insulate pipes in the loft (attic) or roof space.[8]

In the US, the Red Cross says to drain and store outdoor hoses, close the inside valves that supply outdoor hose bibs and open the outside bibs so they drain, add insulation, and open the cabinet doors under sinks so warmer air reaches the pipes.[10] In very cold weather, "let the cold water drip from the faucet served by exposed pipes". Keep the thermostat at the same setting day and night, and if you're away, keep the heat "no lower than 55° F", about 13°C.[10]

Thawing one: two countries, two orders

Here the advice differs, and it is the clearest case in this lesson of the course's question: law or advice, whose, and where? Both are advice, from the bodies this course read: the Met Office, the UK's national weather service, and CCW on one side, and on the other the American Red Cross, a charity. Follow your own country's.

Where they agree: no flame, ever. The Met Office gives its reason: direct heat may damage the pipe and could start a fire.[8] All three sources here give that rule, so it is the one to hold onto. The two UK pages also say to thaw the pipe slowly;[8][9] the Red Cross says to keep applying heat until full water pressure is back.[10]

Where they differ, each gives part of its reasoning. The Red Cross keeps the tap open because running water helps melt the ice.[10] The Met Office opens the cold taps to relieve pressure on the frozen pipe.[8] CCW leaves the cold tap on so thawed water can escape.[9] Neither UK page says in so many words why the stop tap goes off first. CCW doesn't say why the immersion heater and heating go off, and the Met Office's frozen-pipe steps don't mention them. This course won't invent the reasons, and it calls neither country's order the wrong one.

Thawing a pipe you can reach is Yours, if it's your home to repair or your landlord agrees, on the Met Office's and the Red Cross's advice; CCW's steps also say to contact a registered plumber before the pipe bursts.[9] If it has already split, go to lesson 1's burst-pipe order, and then Call someone: CCW says a burst pipe needs a professional plumber.[9] If water is reaching a socket, a light or anything plugged in, or dripping near where you'd plug in a hair dryer or heater, lesson 1's reading applies: don't touch wet switches, sockets or fittings, go to the consumer unit or panel only if you can reach it without standing in water or touching anything wet, and otherwise keep clear and call an electrician.

A leak nobody can see

This is the harder of the lesson's two worked cases, and it stops partway for you.

A family of four in an older single-storey house in Missouri, built over a crawl space, open their February water bill and find it has jumped. They used over 14,000 US gallons in the month, above EPA's 12,000-gallon line for a family of four in a colder month.³ Nobody is taking longer showers.

Step 1: prove the leak. One Sunday morning they read the meter, use no water for two hours, and read it again. It has moved. On EPA's test they probably have a leak.³

Step 2: rule out the toilets. They put food colouring in both toilet tanks and wait ten minutes without flushing. Both bowls stay clear, so neither toilet is leaking from tank to bowl.³

Step 3: rule out the fittings you can see. They check every tap, and the pipes under each sink, for water on the outside of a fitting, as EPA suggests.³ Everything is dry.

Step 4: isolate it. He closes the inside valve to the hose bib, the valve the Red Cross says to close before cold weather.[10] That is Yours: it is the Red Cross's own advice to householders, and it opens nothing.

Step 5: check the isolation worked. Two more quiet hours, and the meter stays still. The leak is on that one branch.

Step 6: who fixes it. A split supply pipe is Call someone: a licensed plumber. This course teaches no pipe repair, and the Red Cross sends people to a licensed plumber for a frozen section they can't reach.[10] Whether the family or their utility is responsible for any given pipe outside is a question for the utility, because US responsibility varies and this course did not research it.

The order is what carries over: prove the leak, then rule places out from the cheapest check upwards, and let the meter tell you when you've found it. Had the same meter moved in a home in England with the meter outside and nothing wrong indoors, United Utilities' advice would send you to the outside supply pipe, which CCW puts on the homeowner's side of the boundary.[6]¹

What people get wrong

"A slow drip wastes almost nothing." A tap dripping once a second wastes more than 3,000 US gallons a year on EPA's figure, and Southern Water puts a slow drip at up to 10,000 litres.³⁵ Each drop is small. There are a great many of them.

"A gallon is a gallon." A US gallon is about 3.8 litres and an imperial gallon about 4.5, WaterSafe's "4.5 litre (one gallon)"² (the 3.8 is this course's conversion). Mix them and your arithmetic is out by a fifth.

"The water company fixes leaks." In England and Wales it deals with the ones on its side of your boundary. From the boundary in, CCW puts the pipe with the homeowner.¹

"The meter moved overnight, so there's a leak." Only if nothing used water in the window. EPA's test is two hours with no water used at all, and a timed dishwasher or a flush in the night spoils it.³

"Thaw it fast with a blowtorch." Every source read here says never: the Met Office, CCW and the American Red Cross.[8][9][10]

"The other country's thawing order is wrong." The UK sources turn the supply off first; the US source keeps the faucet open. Each is advice from its own country's sources, and neither says the other is wrong. Follow your own.

Practice

For your plan

This lesson adds to your seasonal plan: a meter test and a dye test twice a year (EPA's tests), and the stop tap checked every six months (the Met Office). It adds an autumn line before the first frost: pipes lagged and outside taps covered (UK), or hoses drained and the inside valves to the hose bibs closed (US). It adds a WaterSafe plumber's or a licensed plumber's number to your call list. And it adds to your map every pipe that runs where nobody looks.

Connections

Lesson 1, How a house works, and where it switches off, gave you the stop tap or main valve and the burst-pipe order; this lesson used both for a frozen pipe. Lesson 3, Taps and toilets, takes the drips and the running toilet you've now learned to find and prove, and fixes the ones a householder can fix. Lesson 4, Water out: traps, vents and blocked drains, follows the water after it leaves the tap and asks the same question about whose pipe it is, for drains.

From earlier on the Core, Personal Finance lesson 1 put utilities in the housing part of your budget and treated repairs as irregular but inevitable. A hidden leak is both: it raises a metered bill every month until it's found, and the repair is the kind of lumpy cost that lesson told you to plan for.

Go deeper

• EPA WaterSense, "Fix a Leak Week". Free, read here in full. The meter test, the dye test and EPA's leak figures for American homes, in their original form.
• CCW, "Winter advice". Free, read here in full. One page on the signs of a frozen pipe and what to do if one freezes or bursts, for England and Wales.
• American Red Cross, "Preventing and Thawing Frozen Pipes". Free, read here in full. The US side, with the list of which pipes freeze most, which is the most useful thing on it for finding a hidden leak.
• WaterSafe, "What is the minimum water pressure that a water supplier must supply?". Free, read here in full, and short. The bucket guide and the companies' pressure figures.

Sources

1. Consumer Council for Water (CCW), "Who is responsible for my water pipes?", no date shown . Read: full text; re-read on the live page on 25 September 2026. The split of responsibility between the water company and the homeowner, for England and Wales, including the water meter.
2. WaterSafe, "What is the minimum water pressure that a water supplier must supply?". Read: full text; re-read on the live page on 25 September 2026. The bucket guide and its "suitable single service pipe" condition, where pressure is measured, and the companies' 10 metre aim and 7 metre guaranteed minimum as WaterSafe states them. The regulator's own page was not read; the statute is source 11.
3. US EPA WaterSense, "Fix a Leak Week", last updated 13 March 2026 . Read: full text; re-read on the live page on 25 September 2026. The household leak figures, the colder-month bill check, the meter test, the dye test and the faucet figure.
4. US EPA WaterSense, "Statistics and Facts", last updated 11 March 2026 . Read: full text; re-read on 25 September
   2026. Cited only for its 9,400-gallon figure, which differs from the Fix a Leak Week page's.
5. Southern Water, "How to fix a dripping tap" . Read: full text, from the Internet Archive capture 20260515022127, because the live page refused automated readers (it did again on 25 September 2026). Cited here only for its drip figure.
6. United Utilities, "Find leaks inside your home or business". Read: full text; re-read on the live page on 25 September 2026. The share of reported leaks that were toilets, the £400 ceiling and the outside supply pipe, all for its own customers.
7. WaterSafe, "How can I locate my internal stop tap to turn off my water in an emergency?". Read: full text; re-read on the live page on 25 September 2026.
8. Met Office, "What to do if you have a frozen or burst pipe". Read: full text; re-read on the live page on 25 September 2026. The UK thawing order, its reasons for the cold taps and against a flame, that freezing and thawing can burst pipes, and the six-monthly stop tap check.
9. Consumer Council for Water (CCW), "Winter advice" . Read: full text; re-read on the live page on 25 September 2026. Prevention, the signs of a frozen pipe, thawing, and bursts, for England and Wales.
10. American Red Cross, "Preventing and Thawing Frozen Pipes". Read: full text; re-read on the live page on 25 September
    2026. The mechanism, the pipes most at risk, prevention and the US thawing order.
11. The Water Supply and Sewerage Services (Customer Service Standards) Regulations 2008 (SI 2008/594), regulation 17G (England, as amended to 2 July 2025) and regulation 10 (Wales), revised text on legislation.gov.uk . Read: both regulations in full on the live page on 25 September 2026. The 7 metre pressure standard, the definition of a communication pipe, and the payments when the standard is missed.