7 Signs of a Hidden Water Leak (and How to Check in 10 Minutes)
The short version — Watch for unexplained jumps in your water bill, the sound of running water when everything is off, warm spots on floors, musty smells, mould, staining, or a constantly running toilet. Two quick checks find most leaks: read your water meter before and after a two-hour no-use period, and do a 10-minute toilet dye test. According to US EPA WaterSense, the average household’s leaks can waste more than 9,400 gallons a year, and fixing them can cut about 10% off your water bill.
The most expensive leaks are the ones you cannot see. A pipe weeping inside a wall or under a slab can run for months — driving up your bill and quietly damaging framing, drywall and flooring. The good news: most hidden leaks announce themselves if you know the signs, and two simple tests will catch the majority.
7 warning signs of a hidden leak
- An unexplained jump in your water bill with no change in usage.
- The sound of running or trickling water when every fixture is off.
- Warm spots on the floor (a clue to a hot-water line leak under a slab).
- Musty odours, mould or mildew in a specific area.
- Staining or bubbling paint on walls or ceilings.
- A toilet that hisses or runs intermittently on its own.
- Lower-than-usual water pressure with no other explanation.
Test 1: the water-meter check
Find your water meter (often near the curb or in the basement). Make sure no water is being used anywhere in the home, then note the reading. Wait about two hours without using any water and read it again. If the number has changed, you likely have a leak somewhere in the system.
Test 2: the toilet dye test
Toilets are a leading source of silent leaks. Put a few drops of food colouring in the tank (not the bowl) and wait about 10 minutes without flushing. If colour appears in the bowl, water is leaking past the flapper — usually a cheap, easy fix.
Why it’s worth 10 minutes
According to US EPA WaterSense, the average household’s leaks can account for more than 9,400 gallons of water wasted every year, and roughly one in ten homes has leaks that waste 90 gallons or more per day. Fixing easily corrected leaks can save about 10% on your water bill.
When to call a professional
If your meter test says you have a leak but you cannot find it, the leak is likely inside a wall, under a slab, or underground. That is where professional electronic leak detection earns its keep — we locate the leak precisely so the repair is small and targeted, instead of opening up half a room to go looking. (Across Metro Vancouver, where water and the damage a slow leak causes are both costly, catching it early pays off.)
Frequently asked questions
How do I check for a hidden water leak at home?
Two quick tests catch most leaks: (1) read your water meter, wait about two hours with no water use, and read it again — any change suggests a leak; and (2) do a toilet dye test by adding food colouring to the tank and checking the bowl after 10 minutes.
How much water do household leaks waste?
According to US EPA WaterSense, the average household’s leaks can waste more than 9,400 gallons a year, about one in ten homes has leaks wasting 90+ gallons a day, and fixing easy leaks can save roughly 10% on a water bill.
When should I call a plumber for a leak?
If a meter test indicates a leak but you cannot find it, it is likely inside a wall, under a slab, or underground. Professional electronic leak detection can pinpoint it so the repair stays small and targeted.
Sources & further reading
Rebate amounts, fees, and code requirements change over time and by municipality. Figures here were verified against the official sources above as of June 23, 2026; always confirm current details with the program or your local authority before making decisions.
