Venting and condensate for condensing furnaces in Vancouver-area homes

A condensing furnace cools its flue gas below the dew point, so the vent carries cool, wet, mildly acidic gas that cannot go into a metal chimney. The vent must be plastic, sized to the manufacturer's tables (including every elbow as equivalent length), sloped so condensate drains back to the furnace, and terminated where the code and the manufacturer allow. Two-pipe (direct-vent) systems add a combustion-air intake beside the exhaust.

This is the change that surprises homeowners replacing an 80% furnace: the old metal vent and chimney are done, and the new furnace needs its own plastic route to a sidewall termination. If a water heater shared the old chimney, the chimney's future is part of the retrofit scope.

The furnace's secondary heat exchanger produces litres of condensate a day in cold weather. The path runs from the collector box through the trap (which is also part of the flue-gas seal) to a drain or condensate pump. Installations below the drain point, in slab homes, or where the drain runs through unheated space need a pump, careful slope, or winterization per the manufacturer's procedure.

Failure modes are the classic winter no-heat calls: a trap that backs up and floods the collector box, a drain that freezes in an unheated run or at an exterior termination, a sagging vent holding water, or a vent termination blocked by snow, ice or leaves. All of these appear to the furnace as pressure-switch or ignition codes.

Compact lots put vent terminations near property lines, decks, fences and neighbours' windows, so termination clearances are a real design constraint here. Mild but wet winters mean condensate production runs long, and low-lying communities (Richmond, Ladner, parts of Delta) often need condensate pumps where drains sit above the furnace. Crawl-space and slab homes add routing questions that the assessment answers before equipment is ordered.

The gas permit, whether from Technical Safety BC or from the municipalities with their own systems (Vancouver, Richmond, North Vancouver, Maple Ridge, Burnaby, Kelowna), covers the venting and condensate work as part of the appliance installation, and the inspection verifies it.

A complete venting scope names the pipe material and diameter, the route, every fitting counted in equivalent length, the termination location and clearances, the intake arrangement for two-pipe systems, and the condensate route with its drain or pump. It verifies the installed length against the manufacturer's maximum and confirms the slope. Anything less leaves the furnace's certified installation to chance.