Cause · the one with a clean answer

Water heater leaking: how bad it is, whether it is covered, and what to do now

A leaking water heater is the most tractable problem on this site. It is usually one of four things, three of them are cheap, the fourth is the tank itself, and the insurance answer is unusually clean: the water damage is normally covered and the appliance normally is not.

The reason it still ends badly is that a water heater sits on a basement floor, often in a finished room, and a slow leak from the base of a tank can run for weeks before anyone notices it — by which point Health Canada’s 48 hours window closed a long time ago.

Find out which of the four it is

Before anything else, work out where the water is actually coming from. People replace tanks that did not need replacing because the puddle was under the tank and they stopped looking.

The temperature and pressure relief valve. A brass fitting near the top or side, with a discharge pipe running towards the floor. If water is coming out of the end of that pipe, the tank is doing what it is supposed to: relieving pressure. That is either a failing valve, or a genuine over-pressure or over-temperature condition, and the second one is not a wait-and-see item.

The drain valve. A tap at the bottom, usually plastic. They weep. A drip this is the least costly outcome on this page.

The inlet and outlet connections. Two pipes at the top. Corrosion or a loose fitting will run water down the outside of the tank and pool at the base, which is exactly what a failed tank looks like from two metres away.

The tank itself. Water seeping from the base with all of the above dry. Tanks fail from the inside out, by corrosion, and a tank leaking from the body is not repaired — it is replaced. There is no version of this where it gets better.

The diagnostic trick is to dry the whole unit and the floor completely, lay dry paper towel under each candidate, and come back in an hour.

What to do in the first hour

1. Shut the cold supply to the tank. There is an isolation valve on the cold inlet pipe at the top. Turning it stops the tank refilling itself as it empties, which is what turns a leak into a flood.
2. Cut the heat. Electric: the breaker. Gas: the control dial to the pilot or off position. A tank that keeps heating while it drains is the one genuinely dangerous version of this.
3. Photograph it before you mop. The tank, the serial plate, the wet floor and the wet wall, with the date visible.
4. Look at what is around it. Water heaters live next to furnaces, electrical panels and the bottom of finished walls. The damage is rarely the puddle.
5. Then decide whether it is a plumbing call or a restoration call. Both, if the wall is wet.

What your policy will and will not do

This is where a water heater leak is unusually clear-cut. The Insurance Bureau of Canada lists “sudden or accidental water damage caused by indoor plumbing, heating or air conditioning” among what a standard Canadian policy covers, and adds that water damage from an appliance malfunction is covered while the cost of repairing the appliance itself typically is not.

So: the soaked drywall, the ruined flooring, the contents in the storage room — normally covered, subject to your deductible. The new water heater — normally yours.

The word that carries the weight is sudden. A tank that let go on Tuesday is a sudden and accidental escape of water. A fitting that has been weeping into the same patch of subfloor since last winter is much harder to argue, because it is closer to wear and maintenance than to an event. This is the practical reason to deal with a slow leak while it is still boring.

The water from a water heater is clean when it leaves the tank — Category 1 under ANSI/IICRC S500. But category is not fixed. Clean water that sits, warms and passes through building materials degrades, which is precisely the mechanism that turns a three-week undetected drip into a removal job.

How this one turns into a mould conversation

Almost every water heater story that ends expensively ends that way for the same reason: the leak was slow, the space was enclosed, and nobody looked behind the wall.

Health Canada's thresholds are the useful measure here, because they are measurable with a tape rather than argued about. A small area is three or fewer patches, total area under 1 square metre and a homeowner can clean it. A large area is a single patch larger than 3 square metres, and Health Canada recommends a qualified professional assess and clean it.

Two more things Health Canada says, both of which will save you money. Clean visible mould “clean up any visible mould regardless of the type of mould present” — there is no finding out it was the bad kind and no decision that turns on the answer. And “Health Canada does not recommend testing the air for mould”, because an air test does not predict health effects and usually says little about the cause. If somebody wants to sell you sampling before they have found the moisture source, that is the wrong order.

Our page on what mould removal involves goes through the scope questions.

Preventing the expensive version

None of this is elaborate.

Put a pan under it. A drip tray plumbed to a drain converts a category of disaster into a nuisance. In a finished basement it is the single highest-value thing on this list.

Put a leak sensor next to it. A battery water alarm costs less than one hour of a restorer's time and sits on the floor beside the tank.

Exercise the relief valve. Once a year, per the manufacturer's instructions, so that you find out it is seized at a time of your choosing.

Know where the isolation valve is before you need it. Find it now. In the dark, with water running, is a bad time to be learning the plumbing.

Note the age. The serial plate has a date. A tank in its second decade in a finished basement deserves a plan rather than a surprise.

Questions people actually ask

Where to read next

• Washing machines, dishwashers and fridges
• When drying becomes remediation
• How a Canadian water claim actually runs
• Every cause, side by side