How to read a water meter: the black and red numbers
To read a water meter, start with the black figures, read left to right. They are whole cubic metres: the number your bill is worked out from and the one the water company asks for. Most meters in the UK count in cubic metres, shown as m3 on the face, and one cubic metre is 1,000 litres. The red figures, or small red dials, count the part of a cubic metre used since the last black figure turned over.
On a common layout with three red figures, the first counts hundreds of litres, the second tens and the third single litres. So a meter showing 00347 in black and 582 in red reads 347.582 cubic metres, which is 347 whole cubic metres plus 582 litres. Some meters add a small dial or a spinning pointer for fractions of a litre. When the water company wants a meter reading, give the black figures only, unless its form asks for more.
Digital and smart meter displays
To read a digital water meter, look for the total marked m3 on its small screen, usually with figures after a decimal point. Some screens stay blank until you press a button or shine a torch on them, so take one if the meter sits in a dark chamber. The display may cycle through more than one figure, so wait for the one labelled in cubic metres before writing anything down.
Smart meters send readings to the water company by themselves. That is one way a company spots a possible leak: readings that never fall to zero, even in the small hours. You can still read the screen yourself and run the test below. It is worth doing before you ring anyone, because it shows whether the loss is steady and roughly how big it is.
The leak test: two readings with nothing running
Pick a quiet half hour, or take one reading last thing at night and one first thing in the morning. Turn everything off: taps, washing machine, dishwasher, water softener, hose, outside tap. Nobody flushes. If a loft tank is still filling after a shower, wait until it falls silent. Then write down the whole reading, black and red, and the exact time, and take a photo of the dial.
Read the meter again after 30 minutes, with nobody using water in between. If the two readings match to the last red figure, the meter recorded no flow, so there is no leak it can see. If the second reading is higher, water went somewhere while every outlet was closed. Keep both photos: they give us something solid to work from when you call, and the water company may ask what you found.
Turning a reading into litres an hour
Subtract the first reading from the second. Because the red figures are litres, the sum is simple: 0.001 cubic metres is one litre. Say the first reading was 347.582 and the second, half an hour later, 347.594. The difference is 0.012 cubic metres, which is 12 litres in 30 minutes. Double that for a full hour and the meter is recording 24 litres an hour, or 576 litres over a whole day.
For comparison, half a litre a minute is 30 litres an hour. That figure matters for our no find, no fee on home water leaks, because one of its conditions is a leak losing at least that much; full conditions are on our terms page. A leak of 24 litres an hour is real and worth finding, but it is below that line, so the visit would be charged at the price agreed before you book.
What the number tells you
A small movement, a litre or two in half an hour with everything off, can be something indoors: a toilet cistern trickling into the pan, a worn tap washer or a loft tank valve that never quite closes. Bigger, steady losses can come from inside or out, which is why the stop tap test below tells you more than the size does. A large, fast loss tends to give itself away before long as a wet patch, a soft verge or weak pressure at the taps.
The number alone does not say where the leak is. A small leak under a solid floor can do more harm than a bigger one under a lawn, because nobody sees it. A meter that moves only some of the time may be catching an appliance or a tank topping up, so repeat the test before drawing conclusions. If the readings jump about with nothing running, ask the water company about checking the meter.
Inside or outside: using the stop tap to split the test
Once you know water is passing, turn off the indoor stop tap, often found under the kitchen sink, and repeat the pair of readings. If the meter stops, the loss is indoors, somewhere on the pipes, fittings or appliances after the stop tap. If it keeps going at much the same rate, and your meter is outside at the boundary, water is most likely escaping from the supply pipe somewhere between the boundary and your stop tap.
An indoor meter changes this. A meter fitted inside the house, after the supply pipe, never sees water lost under the garden or drive, so with that kind of meter the test can only ever show leaks indoors. If the stop tap is stiff, do not force it, because old ones can snap or start weeping at the spindle. Note it and tell us when you book: our tests rely on a stop tap that turns.
What to do next
Keep your readings, times and photos together. If the water company has written to you, reply with what you found and ask about its leak policy: some companies make an allowance on the bill once a leak on your pipe has been repaired, but the rules differ and are theirs to explain. Then ring us with your figures, plus a rough idea of how many paces it is from meter to stop tap.
For a buried pipe, the ground microphone tells us where the noise of escaping water peaks, and tracer gas takes over on plastic or quiet leaks. A second test must land on the same place before the ground is marked and photographed. We can usually do the repair, priced separately, and repairs are guaranteed for 3 months. Before claiming for trace and access on home insurance, check the policy. The report is laid out for an insurer and is released once the visit is paid for.