What is an underground (main service line) leak?
Your home's water travels through a buried pipe — the service line — from the city water main under the street, up to the main shut-off valve inside your house. That pipe runs anywhere from a few meters to 30+ meters underground. When it cracks, splits at a joint, or corrodes through, water silently saturates the surrounding soil. You won't see a puddle. You won't hear a drip. The only evidence is on your water meter — and on your bill.
Untreated, a moderate underground leak wastes 6,300 to 10,000 gallons per month (≈ 24,000 to 38,000 litres) and can cost hundreds of dollars per quarter on tiered municipal rates. Worse, the saturated soil can undermine your foundation or wash out your driveway over time.
Why this test matters
The animation above shows the only reliable DIY method to detect this kind of leak: use your own meter as the diagnostic instrument. Shut everything off. Watch the meter. Then close the main valve at the house and watch again. The difference between “the meter stopped” and “the meter is still spinning” is the difference between an indoor problem (fixtures, appliances, in-wall pipes) and an outdoor one.
When to call a pro
If the meter is still moving with the main valve closed — you have an underground leak. Don’t dig. Professional acoustic correlation and tracer-gas equipment can pinpoint the exact location within inches, so the repair excavation is small (and so is the bill). The team at Leak.ca has been doing this across BC since 1999.