In a nutshell
In most homes, a sudden jump in the water bill comes from a running toilet. Next most likely are a dripping tap, a leaking outdoor hose bib, a water softener stuck in regeneration, or a hidden leak in a supply line. A simple meter test sorts out which.
Working through it
1. Compare bills
Toronto bills water by metered use. Look at the consumption figure, in cubic metres, on recent bills and compare it with the same period last year. Summer use is often higher because of lawns and gardens. A jump in winter is more telling.
2. Read the meter
Turn off every tap, appliance, softener and irrigation system. Locate the meter beside the incoming pipe in the basement. Note the reading then check the tiny leak dial, often a triangle or star. If it turns with everything off, water is leaving the house.
3. Test the toilets
Tint the water in every toilet tank with food dye. Wait fifteen minutes without flushing. Tinted bowl water points to a leaking flapper. Our running toilet essay shows how to fix it.
4. Isolate the rest
Close each toilet's shut-off and watch the meter again. If it still moves, close other branch valves one by one. The leak lies in whatever section stops the meter when shut.
Clues worth noticing
- A toilet that refills by itself between flushes.
- A hiss in the walls when nothing is running.
- Damp patches in the yard along the water service path.
- Moisture stains on ceilings or around tubs.
- A sump pump running in dry weather, which can mean a leak feeding the pit.
In a house with a basement suite or tenants, consider usage patterns before assuming a leak. More people means more water.
Signals that it needs a licensed plumber
Call if the meter keeps moving with all fixtures and toilets off, if you see water where it should not be, or if you cannot find the source. Our leak detection work starts from the meter and works out from there. For water backing up rather than leaking out, the problem is different; see main drain backup.
If the high bill traces to an underground leak on the property side, the service may need replacing. If you suspect a meter fault, contact the City of Toronto through 311; they can check the meter and explain billing adjustments where policy allows. Renters with a water heater on the bill may also find our rental water heater notes useful.
Calls we field, answered plainly
Can a dripping tap really raise the bill?
A slow drip adds up over months, though a running toilet usually wastes far more.
Who do I call about a broken water meter?
Contact the City of Toronto through 311 to have the meter checked.