Why the Bottom Is Where Leaks Show Up
A boiler is a sealed loop of water under pressure, wrapped in pipes, pumps, valves, and seals. When any of those components weeps, gravity pulls the water down — so the bottom of the casing or the floor beneath the unit is almost always where you'll first notice it, even if the actual fault is higher up inside.
That means "leaking from the bottom" is a symptom, not a diagnosis. The job is to trace the water back up to its true source. In Greater Vancouver homes, the usual suspects are the pump, the auto air vent, the pressure relief valve discharge, corroded internal pipework, or — in the worst case — the heat exchanger.
If the water under the boiler is accompanied by a gas smell or a sounding CO alarm, stop. Leave the home, call FortisBC at 1-800-663-9911 or 911 from outside, then call us at 604-359-1081.
Pump and Seal Leaks
The circulator pump moves heated water around your radiators or in-floor loops. It has a shaft seal that, over years of heat cycling, can perish and begin to weep. A pump leak typically shows as water directly beneath the pump body, sometimes with light staining or limescale crusting on the housing.
Union fittings and gaskets on either side of the pump are another frequent source. They can loosen slightly with thermal expansion or the rubber can harden and crack. Re-sealing or replacing the affected gasket is often a straightforward repair when caught early.
If the pump itself is the source rather than its seals, replacement is usually the right call — a leaking pump can also be on its way to a bearing failure, which would leave you with no heat.
Pressure Relief Valve and Expansion Vessel
Many bottom leaks aren't internal at all — they're the pressure relief valve doing its job. When system pressure climbs too high, the PRV opens and pushes water out through a discharge pipe that often runs down and out near the base of the unit. If you see water at the bottom and your pressure gauge reads above 2.5 bar, this is the likely answer.
The root cause is usually a waterlogged expansion vessel. The vessel uses an air cushion to absorb the expansion of heated water; when that cushion is lost, pressure spikes every time the boiler fires and forces water out the relief valve. Recharging or replacing the expansion vessel solves it properly. Simply bleeding pressure off only buys a day or two.
Corrosion and Heat Exchanger Faults
Metro Vancouver's soft water is gentle in some ways but slightly acidic, and over a decade or more it slowly eats at metal joints and internal pipework. Pinhole corrosion leaks low in the unit will drip straight to the floor. These are repairable if isolated to a fitting, but widespread internal corrosion in an aging boiler signals the unit is near end of life.
The most serious bottom leak is a breached heat exchanger. If the leak is accompanied by rust-coloured water, frequent pressure loss, and the boiler locking out, the heat exchanger may be cracked or corroded through. On older units the cost of a new heat exchanger often approaches the cost of a new boiler, so we'll give you an honest repair-versus-replace assessment rather than throwing money at a dying unit.
What to Do Now
Turn the boiler off at its switch, place a towel or tray to protect your floor, and note the pressure gauge reading. Don't keep re-pressurising a system that's actively leaking — you're just feeding fresh corrosive water in.
Then call GasBoilers.ca at 604-359-1081. As a CanroHeat Division, we cover Vancouver, Burnaby, Surrey, Richmond, Coquitlam, the North Shore and the rest of the Lower Mainland with same-day and weekend availability where possible. We'll trace the leak to its source, fix what's worth fixing, and tell you plainly when replacement is the better value.