My bill jumped in the summer. Is that a leak?

It may be, and a summer jump on its own is not evidence either way, because a garden, a paddling pool, more showers and more visitors all raise real use at the same time of year. The way to tell is not to compare bills but to run an overnight meter test, which measures the property with nothing running.

Why does this site default garden use to zero?

Because no sourced average was found for it, and a default above zero would raise the expected use figure for everybody, including households with no garden. That would make a real leak look like ordinary summer behaviour, which is the more expensive of the two possible errors. The field is adjustable, so put your own figure in.

How do I estimate my own garden use?

Time the hose into a bucket to get litres per minute, then multiply by how long you actually water for and how often. Like the fixtures, it is your own number in a few minutes rather than an average of somebody else's garden.

Does a leak get worse in summer?

It can appear to. Ground movement in dry weather can open up an existing supply pipe fault, and higher mains pressure pushes more water through any given hole. So a genuine leak can grow in summer at the same time as legitimate use rises, which is exactly why the two need separating by measurement rather than by inference.

What counts as a big seasonal swing?

Larger than most people expect. Filling a modest paddling pool once is comparable to a person's entire daily use, and regular hose watering can add more than an extra occupant. Neither is a leak, and both will show on a bill.

Seasonal use, garden watering, and telling them apart from a leak

A summer rise in metered volume is the most common false positive in a leak enquiry, and it is separable from a leak in one night. Seasonal use is intermittent, because somebody has to turn a tap on, and a leak is continuous. An overnight meter test with everything closed distinguishes them regardless of the time of year.

Last reviewed 14 August 2026

The short answer

Seasonal use and a leak look identical on a bill and completely different on a meter, because they differ in a way a bill cannot show: when the water moves.

	Seasonal use	A leak
When it happens	When somebody turns something on.	Continuously, including at four in the morning.
On a quarterly bill	A higher volume.	A higher volume. Indistinguishable.
On an overnight meter test	Nothing. Nobody is watering at 3 am.	A steady movement.
Across the year	Rises and falls with the weather.	Steady, or gets worse.

The distinction that separates them

That third row is the whole page. One night of not using water settles a question that no amount of comparing bills can, because the bill records a total and the test records a rate.

How this works in practice

Four things raise real household use in summer, all of them legitimate, and all of them capable of producing a bill that looks like a leak.

Garden watering, which is the largest of the four for most households with a garden and can exceed the daily use of an extra occupant.
Filling a paddling pool or topping up a pool, which is a large single volume rather than a rate.
More showers, and longer ones, in hot weather.
More people at home, and visitors, over the summer.

Every one of those is intermittent. Somebody has to be there and turn something on. That is what makes them separable from a leak, which needs nobody present and does not stop at night.

So the test is not to compare this summer against last summer. It is to close everything for a night and read the meter twice. take two readings over a measured interval is unaffected by the season, because nothing legitimate is running during it.

What changes the answer

Three things, and the third is the one that catches people who have already run a test.

An automatic irrigation timer, which is the exception to everything above. It runs at night, it needs nobody present, and it will read exactly like a leak on an overnight test. Isolate it before testing.
An automatic pool top-up, for the same reason and with the same fix.
A leak that genuinely worsens in summer. Dry ground moves and can open an existing supply pipe fault, and higher mains pressure pushes more through any hole. So a real leak can grow at the same moment legitimate use rises.

The first two are why "close everything" has to include the things that turn themselves on. A test that leaves an irrigation timer live measures the timer.

Assumptions and sources

Water resources 2024 to 2025: analysis of the water industry's annual water resources performance

Environment Agency · primary source

Household per capita consumption: 136.5 l/person/day
Household per capita consumption, prior year: 137 l/person/day
Household per capita consumption, dry-year adjusted: 140.3 l/person/day
National leakage: 2617 Ml/day
National leakage as share of water put into supply: 19 %

PR24 common performance commitments: per capita consumption (PCC), version 2.1

Ofwat · primary-standard source

PCC formula: (measured household consumption + unmeasured household consumption) / total household population l/person/day

Litres in a cubic metre

Exact by definition

SI definition. The litre is defined as one cubic decimetre, so one cubic metre is exactly 1,000 litres.

Days used for an annual figure

Editorial convention

Annual figures on this site are a daily rate multiplied by 365. Leap years are not modelled, so a leap year is understated by one day, which is 0.27 per cent.

Garden watering allowance

Illustrative assumption, editable above

Illustrative assumption, defaulting to zero. Garden use varies with the weather, the size of the garden and whether it is watered by hose or by can, and no cited average has been sourced. A default of zero means the expected figure is never quietly inflated. Put your own figure in if you water regularly.

No garden use figure is quoted here, because none has been sourced. Garden use varies with the weather, the size of the garden, and whether it is watered by hose or by can, and no cited average was found.

The site's garden allowance therefore defaults to ZERO rather than to a plausible-sounding number, and that direction was chosen deliberately. A default above zero would raise expected use for every household, including those with no garden, and would make a real leak look like ordinary summer behaviour. Of the two possible errors, hiding a leak is the expensive one.

Everything else on this page is mechanism rather than measurement: that seasonal use requires somebody to turn something on, that a leak does not, and that an overnight test therefore separates them. None of that is a statistic and none of it is cited as one.

What to do next

Three things, and the first replaces a month of wondering.

Run an overnight meter test with everything closed, including any irrigation timer and any automatic pool top-up. One night answers the question the bill raised.
If you want a figure for your own garden use, time the hose into a bucket and multiply. It takes five minutes and gives you a number rather than an estimate.
Compare annual volumes rather than quarterly ones if you are comparing bills at all. A year contains one of every season, so two years are comparable in a way two quarters are not.

And if the overnight test is clean, the summer rise was use rather than loss, which is a real answer. compare your annual consumption against that figure puts that use in context against the national average.

Common questions

My bill jumped in the summer. Is that a leak?: It may be, and a summer jump on its own is not evidence either way, because a garden, a paddling pool, more showers and more visitors all raise real use at the same time of year. The way to tell is not to compare bills but to run an overnight meter test, which measures the property with nothing running.
Why does this site default garden use to zero?: Because no sourced average was found for it, and a default above zero would raise the expected use figure for everybody, including households with no garden. That would make a real leak look like ordinary summer behaviour, which is the more expensive of the two possible errors. The field is adjustable, so put your own figure in.
How do I estimate my own garden use?: Time the hose into a bucket to get litres per minute, then multiply by how long you actually water for and how often. Like the fixtures, it is your own number in a few minutes rather than an average of somebody else's garden.
Does a leak get worse in summer?: It can appear to. Ground movement in dry weather can open up an existing supply pipe fault, and higher mains pressure pushes more water through any given hole. So a genuine leak can grow in summer at the same time as legitimate use rises, which is exactly why the two need separating by measurement rather than by inference.
What counts as a big seasonal swing?: Larger than most people expect. Filling a modest paddling pool once is comparable to a person's entire daily use, and regular hose watering can add more than an extra occupant. Neither is a leak, and both will show on a bill.