Short answer: Usually a leak. Severn Trent says its test records in recent years show no meters failing by over-recording; meters that fail tend to under-record. Run the flow test first: everything off, read the meter, no water for three hours, then read it again. A higher reading means water is escaping.
Water leak or faulty meter is the first question most people ask when a bill doubles. It is a fair question, but the evidence points one way. A leak is far more common than a meter that runs fast.
What Severn Trent says about its meters
Severn Trent‘s meter policy says its test records in recent years show no meters failing by over-recording; meters that fail tend to under-record. It also lists the reasons a bill can be higher than expected: a garden sprinkler, more people at home, building work, a new appliance, more time at home, or a leak.
It lists two ways a bill can be wrong without anything leaking: a misread meter, and crossed meters, where your bill comes from someone else’s meter. Both are worth ruling out, and neither needs a meter test.
The checks, in order
| Check | How | What it tells you |
|---|---|---|
| Serial number | Compare the number on your meter with the one on your bill | Rules out a crossed meter |
| Reading | Photograph the meter and compare with the bill | Rules out a misread |
| Flow test | Everything off, read the meter, no water for three hours, read again | Any rise means water is escaping |
| Stop tap test | Close the internal stop tap and watch the meter | Still moving: leak on the supply pipe. Stopped: leak inside |
| Inside check | Toilets, taps, outside taps, appliances | Finds most internal leaks |
Meter still moving with everything off?
The leak is on your supply pipe. Get it located.
If the flow test shows a leak
With the internal stop tap closed, a moving meter means the water is escaping between the meter and the house, on the buried supply pipe. That pipe is yours from the boundary. The leak is found with underground water leak detection, and once it is fixed you can claim Severn Trent‘s leakage allowance.
If the meter stops when the internal stop tap is closed, the leak is inside. A toilet cistern trickling into the pan is a common culprit, and easy to miss.
If the flow test is clean
If the meter doesn’t move during the flow test and the readings match the bill, the extra use was probably real, or it came from an intermittent leak such as a cistern that only runs sometimes. Only then is a meter accuracy test worth paying for. It typically costs £70 plus VAT, charged only if the meter proves accurate.
For what to do about a leaking meter itself, see water meter leak.
Bottom line
Suspect a leak before the meter. Do the flow test, then close the internal stop tap to tell inside from outside. Only pay for a meter test once the flow test and a leak check come back clean. Call 0115 839 0791, 9am–7pm, 7 days.