A water meter that moves with every tap off means water is leaving the system somewhere. A slow creep usually points to a toilet, dripping tap or weeping joint; a steady spin to a split pipe. Close the internal stop tap: if the meter stops, the leak is indoors; if it keeps going, it is on the buried supply pipe.
You have turned off every tap, nobody is in the shower, the washing machine is silent, and the little wheel on the water meter is still turning. It might be crawling round so slowly you had to stare at it to be sure, or it might be spinning like it means it. Either way, water is going somewhere you did not send it. The meter only registers flow, so it cannot lie about that. What it cannot tell you is where the water is going. This guide covers how to read the meter properly, what the speed of movement suggests, the usual culprits in order, and the one test that splits the house from the garden. If the tests point to a hidden pipe, our hidden leak survey takes over from there.
First, read the meter properly
Most meters in Cornwall sit in a boundary box near the lane or pavement, under a small plastic lid. Some older houses have theirs indoors, next to the stop tap. Lift the lid, wipe the face and use a torch. You will see three things.
- The black digits. These count cubic metres, and one cubic metre is 1,000 litres. This is the figure your bill is based on.
- The red digits or small dials. These count the fractions of a cubic metre, in effect litres. A slow leak shows here long before it moves the black numbers.
- The flow indicator. A small star, triangle or wheel on a mechanical meter, or a droplet or flow icon on a digital one. It moves whenever water passes, even a trickle too small to hear.
Write the full reading down, red digits included, and note the time. Two readings an hour or more apart tell you how much water is going, which matters later.
Slow creep or a proper spin
The speed of the indicator is a rough guide to the size of the leak, and the size of the leak is a rough guide to what it is. Use the table as a starting point, not a verdict.
| What you notice | Most likely cause | What to do |
|---|---|---|
| Indicator creeps, a full turn every minute or more | Toilet fill valve, dripping tap, weeping compression joint | Check every toilet and tap first. Close their isolating valves one at a time. |
| Indicator turns steadily, red digits climb hour by hour | Split on a pipe under a floor or underground | Do the stop tap test, then book a survey. |
| Indicator spins fast, black digits move within the day | Burst or large split, often on the supply pipe | Close the stop tap, ring South West Water if it still moves. |
| Indicator stops and starts on its own | Toilet topping up, boiler filling loop, water softener regenerating | Watch which appliance coincides with the movement. |
| Indicator moves, stops after a few minutes, stays still | A cistern or tank finishing its refill | Not a leak. Wait 30 minutes and look again. |
The usual culprits, most likely first
Work through these in order. Most people find their answer in the first two.
- A toilet. A fill valve that never quite shuts, or a flush seal that lets water trickle into the pan, wastes water silently all day. Put a few drops of food colouring in the cistern and wait ten minutes without flushing. Colour in the pan means it is leaking. Modern push-button loos are the worst offenders, as our guide to a dual flush toilet that leaks silently explains.
- A tap, including the outside one. A drip you can see is easy. A drip from a garden tap behind the shed, or a hose left connected with a leaking gun, is easy to forget.
- The heating system topping itself up. If the boiler’s filling loop was left open, or an automatic filler is fitted, a heating leak draws mains water every time the pressure drops. A boiler that needs topping up every few days is the giveaway; see why a boiler keeps losing pressure.
- Appliances and softeners. A washing machine inlet valve that weeps, a plumbed-in fridge, or a water softener stuck in a regeneration cycle can all move the meter.
- The supply pipe. The buried run from the meter to your house. Old alkathene, iron or lead pipes split at joints, at bends and where they pass under a drive. Nothing shows at the surface in free-draining ground.
- A pipe under the floor. A pinhole in a hot or cold pipe under a solid floor, or in a wall, can run for months. The first sign is often a warm patch, a musty smell or a skirting board that swells.
The isolation test
This is the test that does most of the work. Find your internal stop tap. In most homes it is under the kitchen sink; in older cottages it may be in a cupboard by the front door, under the stairs or in the utility room. Turn it clockwise until it stops, wait half a minute for the pipes to settle, and go back to the meter.
If the indicator has stopped, the leak is somewhere after the stop tap: inside the house, on the plumbing or the heating. Now close the isolating valves on each toilet and each appliance in turn, checking the meter after each one. When the indicator stops, you have found the fitting.
If the indicator keeps turning with the stop tap closed, the leak is on the buried supply pipe between the meter and the stop tap. For a slow leak, run the check over a whole night rather than an hour: our guide to the full overnight meter test covers how to turn the readings into litres per hour.
What the result means for who pays
South West Water look after the water main, the communication pipe and the meter up to the boundary stop valve. Everything from there into the house is yours. So a leak that keeps the meter turning with the stop tap closed is on your supply pipe and your responsibility to repair, though South West Water offer a leak allowance on a first supply-pipe leak, subject to their conditions, once it has been fixed. A leak inside the house is yours too, but your buildings insurance may include trace and access cover for finding it. Keep every meter reading and photo you take now, because both routes will ask for them.
Why Cornish homes throw up the odd result
Cornwall’s soft water is kind to pipes compared with the hard water further east, but the housing stock is older and the pipe runs are longer. A terrace in Truro or Penryn may have a shared supply pipe with a split that shows on several meters at once. A granite cottage with pipes buried in a slate floor can leak for a season with nothing to see, because the water drains straight into the ground. And a farmhouse with two hundred metres of alkathene across a field will keep a meter turning while the field looks perfectly normal. Our Truro leak detection page covers the properties we survey in the city.
When to stop testing and get it found
Once the stop tap test has told you which half of the system the leak is in, more testing will not narrow it further. Chasing a buried leak with a spade, or lifting floors on a hunch, is how a small repair turns into a big one. A survey uses acoustic listening to hear the escape along the pipe, tracer gas for quiet plastic pipes, and thermal imaging and moisture mapping indoors, so the repair needs one hole in the right place. We are Cornwall’s leak detection specialists, and our report is written for your insurer and South West Water as much as for you.
Frequently asked questions
Why is my water meter spinning with everything off?
Because water is passing through it, and if nothing in the house is using water, it is escaping somewhere. The usual causes are a toilet that never stops filling, a dripping tap, a heating system topping itself up, a split on the underground supply pipe, or a pinhole in a pipe under a floor.
Does a very slow-moving dial still mean a leak?
Yes. The small star or triangle on the meter face is designed to catch flows too small to move the main digits. A dial that creeps round with everything off is often the earliest sign of a slow leak. Watch it for a full hour, or overnight, to be sure it is continuous rather than a cistern finishing its refill.
How do I know if the leak is inside or outside?
Close your internal stop tap and look at the meter again. If the indicator stops, the leak is inside the house, after the stop tap. If it keeps moving, the leak is on the buried supply pipe between the meter and the house. That single step tells you where to look and who is responsible for the repair.
Can a toilet really make the meter move?
Easily. A fill valve that does not fully close, or a worn flush seal, lets water run into the pan continuously and silently, and it can waste hundreds of litres a day. Put a few drops of food colouring in the cistern, wait ten minutes without flushing, and look for colour in the pan.
The meter moves with the stop tap closed. Who pays for the repair?
That points to your supply pipe, which is the homeowner’s responsibility from the boundary stop valve into the house. South West Water offer a leak allowance on a first supply-pipe leak once it is repaired, subject to their conditions, so keep your meter readings from before and after the fix.
Meter will not sit still?
If the isolation test says the leak is hidden, we trace it, on the supply pipe or under the floor, with acoustic, tracer gas and thermal equipment, and leave you with a report your insurer will accept.
