The real cost of a water leak in a vacant home

When people picture water damage costs, they picture the plumber’s invoice. In a vacant property, that’s usually the smallest number on the pile.

The water itself

Municipal water and wastewater rates in Ontario commonly combine to $5–6 per cubic metre. A modest running leak — a failed toilet flapper, a split supply line dribbling — can move 10–30 m³ a month unnoticed. A serious one moves more: at our own property, an underground leak ran 2,413 m³ in a single month, a $14,811.25 bill. (We publish the redacted bill on our story page.) Water is metered honesty: every litre that escapes gets invoiced.

Remediation, not repair

The pipe fix might be a few hundred dollars. What multiplies in a vacant home is time-on-surface: water that sits soaks subfloor, wicks up drywall, and finds insulation. Industry restoration pricing for a wet basement typically starts in the low thousands and climbs with every day of saturation. In our October 2024 survey of 50 Ontario STR operators, average direct costs per incident ran $1,000–1,500 — and those were mostly caught incidents.

The mould clock

Mould growth can establish on damp materials within days. Once it does, the job changes category: containment, removal of affected material, and air-quality verification. Vacancy is what gives the clock time to run — nobody smells damp in a house nobody enters.

The income tail

For a rental, add the bookings cancelled during remediation, and — if a guest discovered the problem — the review. Our survey put one bad review at roughly $3,000 in lost future bookings. The leak stops costing you when the last cancelled week passes, not when the pipe is fixed.

The honest summary

A leak’s cost is mostly a function of detection delay. Caught at hour one, it’s a service call. Caught at week three, it’s a restoration project with an income tail. That arithmetic — not the hardware — is the entire argument for continuous flow monitoring on a property nobody’s living in.