Buying a house: what a viewing does not show about the plumbing
A house is viewed in thirty minutes. Its plumbing is almost entirely hidden — and it is the costliest part to put right afterwards.
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What a viewing shows, and what it hides
During a viewing you see taps that run and toilets that flush. That is reassuring, and it is very little: neither check says anything about the state of the main drain, the material of the water service line or the real age of the water heater.
A finished basement is the most misleading case. Tidy finishing covers exactly the places where a problem would show: the base of the walls, access to the drain, the area around the floor drain.
It is also the part of a house whose repair costs the most. Replacing a water service line or a main drain means excavation — an expense of a different order from redoing a bathroom.
The questions to ask the seller
These questions cost a conversation. The answers, or their absence, already tell you where to look more closely.
- Has there ever been a backup or water damage, and what was done about it?
- Does the house have a backwater valve, and when was it last checked?
- How old is the water heater, and is there still an installation invoice?
- Has the pipework been redone, in whole or in part, and when?
- Where is the main shut-off valve, and does it still work?
When a plumbing inspection is worth its cost
A general pre-purchase inspection remains essential: a building inspector covers roof, structure, foundation and electrical. But that mandate spans the whole building, which leaves little room for examining one system in depth.
A separate plumbing inspection picks up where the first stops: condition and material of the water service line, main and branch drains, age of the water heater, pressure at several points, traces of past damage. On older stock or a lot with large trees, a camera inspection of the drain settles in minutes a question that would be costly to discover after signing.
The right moment is after an offer conditional on inspection: the report can still change the price or the terms. The two inspections are complementary, not interchangeable.