The bill found it. What it implies: a pressurised supply leak, losing measurable volume continuously — and running for at least one full billing period, frequently longer before anyone reacted. Where it's likely: a toilet passing water silently, an irrigation line or stuck valve, a service line between the boundary and the building, or a slab leak. All four can lose a large volume with nothing visible indoors. Urgency: moderate to high, and the rate decides. Start with a meter test and a toilet dye test — between them they explain a large share of unexplained bills.
A smell found it. What it implies: moisture has been present long enough for materials to change. A musty smell is not an early warning — it means something has been damp for a while. Where it's likely: inside a wall cavity, under flooring, or in a confined space with poor ventilation. Urgency: high, because by the time it smells, the damage has started. Worth ruling out first: a dry trap in an unused fixture, which smells of sewer gas rather than mustiness and costs two litres of water to fix.
A sound found it. What it implies: water moving under pressure with nothing switched on — and it's usually the earliest genuine warning on this list. Where it's likely: a supply line inside a wall, under a floor, or beneath a slab. Slab leaks are frequently found this way, because there's nothing to see and something to hear. Urgency: high, and this is the best possible moment. The leak is confirmed, it's substantial enough to hear, and nothing has been damaged yet.
A stain found it. What it implies: water has escaped, travelled, soaked through a material, and reached a visible surface. That takes time, which is why a stain is a middle-to-late warning rather than an early one. Where it's likely: rarely directly above or behind the mark. Water runs along joists, beams, and pipe runs before it drops, so the stain is where it finished rather than where it started. Urgency: high, and it's already a repair-plus-restoration job. Photograph it before anything is opened or dried.
A feeling found it — a soft floor, a warm patch, a damp carpet. What it implies: prolonged contact between water and building materials. A soft or cupped floor means the subfloor has been wet for a long time. Where it's likely: beneath the floor, or under a slab. A warm patch on a floor is a strong indicator of a hot-side slab leak and worth acting on quickly — pressurised water under concrete erodes what's supporting it. Urgency: high, and the damage cost is already accruing.
Somebody else found it. A neighbour, a downstairs unit, a property manager, a meter reader, or a home inspector. What it implies: the evidence reached somewhere you don't look — or somewhere that isn't yours. In multi-unit buildings, the unit reporting the water is frequently not the source. Urgency: high, and there's a coordination element. If you're in a shared building, tell management at the same time you call us, because access to the actual source may not be yours to arrange.
Nobody found it — you opened something for another reason. Renovation, a flooring change, or a different repair. What it implies: you got lucky. This is the only entry on the list with no duration attached to it, and it's the cheapest possible discovery. Urgency: deal with it while it's open. The access is already paid for by another trade, and it will never be cheaper.