If your water meter turns when all the taps are closed, it may be a hidden leak. The meter is a flow meter: it records all the water that passes into your installation, whether visible or not. This article explains how to carry out the meter test yourself, what the meter does and does not measure, and when you need professional help.
How to read your water meter
The first step is to know what type of meter you have and how to read it correctly.
Analogue (mechanical) meter
This is common in homes. It has a dial with numbers showing the cubic metres used and, very importantly, a small wheel or red triangle (flow indicator) that turns whenever water passes, however little.
How to read it:
- Black numbers: whole cubic metres.
- Decimals: fractions of a cubic metre; depending on the model they usually appear on a separate dial or in a different colour.
- Red wheel/triangle: if it turns, even slowly, water is passing.
Digital (electronic) meter
It has an LCD screen showing consumption in m³ or litres. Some advanced models include instantaneous flow indicators and alerts for abnormal consumption.
The meter test: how to check for a leak in 5 steps
Step 1: Close all points of use
Make sure no water is being used anywhere:
- Close all taps (kitchen, bathrooms, laundry)
- Check that the toilet cistern is not refilling
- Switch off the washing machine and dishwasher if they are connected
- If you have automatic irrigation, turn it off
- If you have a storage water heater, check it (its safety valve may be dripping)
- If you have a pool with automatic filling, close it
Step 2: Find your meter
In a detached house it is usually in a box on the pavement or in the garden. In flats, it is in the building's meter room (ground floor or basement).
Step 3: Note the exact reading
With all points of use closed, note the full reading including the decimals. Check whether the wheel or red triangle is turning.
Step 4: Wait without using water
Choose a period when nobody will use water (for example overnight, with no scheduled irrigation or filling). The longer the interval, the easier it is to see the difference.
Step 5: Read again and compare
After the interval, note the new reading. If it is identical, there is no appreciable loss. If there is a difference, there is consumption with no apparent use, and you should act according to its size:
- Small difference: check cisterns, taps and visible valves. If you find nothing, contact a professional.
- Noticeable difference: it may be a concealed or buried pipe. In that case, it is advisable to request professional detection.
- Large difference: it may be a major leak. Close the main valve and contact a professional as soon as possible.
What the meter measures and what it does not
One point that causes confusion: the meter measures all the water entering your installation, but some consumption affects the meter and some does not.
What the meter DOES measure
Water passing through the installation under mains pressure: taps, showers, appliances (washing machine, dishwasher), toilet cisterns, the heating circuit, automatic irrigation connected to the mains, leaks in concealed pipes, and drips from water heater safety valves.
What the meter does NOT measure (although there may be a leak)
Drains: water that goes down the drain has already passed through the meter when it came in, so a leak in a drainage pipe does not make the meter turn.
Pool with an independent meter: if it has manual filling or its own meter, its leaks usually do not affect the home's main meter.
How to narrow down the leak by zone
If the meter turns with no visible consumption, you can try to narrow down the affected area by closing sectional valves if your installation has them:
- Close the home's main valve: if the meter stops, the leak is inside your installation. If it keeps turning, it may be before that valve (the service connection or the public network), and you should inform the water company.
- Close the irrigation valve: does it stop? Then the leak is in the automatic irrigation.
This do-it-yourself zoning helps you define the area better for the professional diagnosis, but it does not pinpoint the exact leak.
Common causes of a meter that turns on its own
Besides leaks in concealed pipes, there are other common causes that make the meter move with no apparent consumption:
Faulty toilet cistern
This is a frequent cause. The discharge valve wears out and lets water slowly through into the toilet. The cistern empties, the level drops and the float activates automatic refilling. This cycle repeats periodically and consumes water continuously. The test is simple: lift the lid of the cistern and look at the mechanism.
Leak in hot water pipes
A micro-leak in the hot water network can be sustained and go unnoticed, especially if there are defective joints or micro-cracks in the fittings. Besides the continuous consumption recorded by the meter, these leaks can cause noises in the pipes or damp on the walls.
Leak in a concealed cold water pipe
Copper, iron or multilayer pipes can develop microscopic cracks caused by corrosion, flexing of the material, or welding defects. Water seeps slowly into the floor slab or walls, with no visible damp for some time.
Automatic irrigation with an underground leak
An irrigation system with a buried leak can drip for hours without you noticing, especially at night. The meter records the water continuously.
When you need professional help
Call a specialist if:
- The meter turns and you cannot find the source of consumption after checking taps, cisterns and visible points.
- There is damp on walls or floors with no visible origin.
- The leak is under the floor, in the garden, or in a concealed pipe.
- You suspect a leak in the pool.
- The extra consumption is significant.
A professional can use pressure tests, an electronic geophone and tracer gas to pinpoint the leak accurately, without having to break walls blindly.
Other causes of a higher bill (without a leak)
If the meter is not turning but the bill has gone up, there may be other causes:
- Change in consumption habits: a new person in the home, longer showers, frequent use of the washing machine.
- Reading error or a change of tariff band.
- Leak in the public network (before your meter): inform the water company so that they can check it.
Prevention: avoid future leaks
- Check your meter periodically; it costs nothing.
- Replace flexible hoses periodically.
- Excessive network pressure can damage seals; a professional can measure it.
- Check cisterns annually.
If your meter turns on its own and you need to locate the leak, request a quote or contact a specialist in detection without construction work. See also our guides on what to do about a leak at home and the detection technologies available.
