What Is a Gas Line Drip Leg and Does My Boiler Need One?

Published: July 21, 2026 — CANRO Heating & Cooling — Greater Vancouver, BC

Purpose

A drip leg (also called a sediment trap) is a short vertical pipe section at the bottom of the gas line before the boiler. It catches debris, moisture, and sediment from the gas supply before they enter the gas valve. Dirt in the gas valve can cause sticking and failure.

BC Code Requirements

BC Gas Code requires a drip leg on the gas line serving any appliance with a gas valve. The drip leg must be at least 3 inches long and located as close to the appliance gas valve as practical. Missing drip legs should be added during boiler replacement.

Inspection and Maintenance

Drip legs require no routine maintenance — debris settles and stays in the leg. If you smell gas near the boiler gas connection, the drip leg or gas piping may need inspection. A drip leg is not a substitute for a gas filter on the supply line.

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Safety Reminder

If you smell gas, suspect carbon monoxide or believe there is an immediate danger, leave the property and contact emergency services or the appropriate gas emergency authority. Do not remain inside — exit the building immediately and call for help from outside.