Short answer: if your usage didn't change and your bill did, water is going somewhere you can't see. The meter test below will tell you whether there's a leak in about twenty minutes, for free.
The Meter Test
Turn off every tap, appliance and ice maker in the house. Don't flush anything. Then go and look at your water meter and note the reading — or watch the small flow indicator, the little dial or triangle that spins when water moves.
Wait thirty minutes without using any water, then look again. If the reading moved, water is leaving the system while nothing is switched on. That's a leak. If it didn't move but your bill is still high, the culprit is usually something that leaks only some of the time — most often a toilet.
The Usual Suspects, In Order
Toilets. A worn flapper seeps silently into the bowl and can waste hundreds of gallons a day. Put a few drops of food colouring in the tank, wait twenty minutes without flushing, and check the bowl. Colour in the bowl means the flapper is passing.
Supply lines and shut-off valves. The braided lines behind toilets and under sinks fail with age, and the valves seize or weep at the packing nut. These are cheap parts that cause expensive cabinet damage.
Water heater. Look at the floor around and under it, and at the connections on top. A pinhole on a heater line drips onto the floor for months before anyone notices.
Outside spigots and irrigation. A hose bib that drips inside the wall, or a stuck irrigation valve, will move a bill without ever showing itself indoors.
Under the slab. The hardest one. Warm patches on the floor, the sound of running water with everything off, or unexplained damp are the signs. Slab leaks need locating properly before anyone opens concrete.
What Actually Costs You
The dramatic leaks aren't usually the expensive ones — a burst line gets fixed the same day because you can't ignore it. The costly ones run quietly for months: a slow drip inside a vanity, a seeping supply line behind drywall, a heater weeping onto a finished basement floor. By the time there's a stain, there's usually rot behind it.
That's the honest case for calling early. Finding a leak is cheap; replacing a subfloor isn't.
When to Call Us
If the meter moved and you can't see why, or you've found damp with no obvious source, that's the point where guessing gets expensive. We locate the source before opening anything, so the repair takes out the smallest amount of house that fixes the problem — see leak detection and repair.
Buying a house and worried about what's behind the walls? A pre-purchase plumbing inspection checks the whole water path before you close.
FAQs
How much of a jump means a leak?
There is no single number, but a bill that rises with no change in how you're using water is the signal. A steady climb over two or three cycles matters more than one odd month.
Can I test for a leak myself?
Yes, roughly. Turn off every fixture and appliance that uses water, then check the meter. If the dial still moves, water is going somewhere. That test won't tell you where, but it tells you there's something to find.
What if the meter is still and the bill is high?
Then it's usually a fixture that leaks intermittently — a toilet flapper that seeps, or an irrigation valve. A running toilet can waste more water than most people believe.
Is a hidden leak urgent?
A leak filling a room is — call the 24/7 line. A slow one isn't an emergency, but it shouldn't wait months, because slow leaks are the ones that quietly ruin subfloor, cabinets and drywall.