Water Heater Gas Line Sediment Trap — Purpose and Maintenance

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

Purpose of the Sediment Trap

A sediment trap (also called a drip leg) is a short vertical pipe section at the bottom of the gas line before the water heater gas valve. It catches debris, pipe scale, and moisture from the gas supply before they can enter and damage the gas valve. Without it, debris can cause the gas valve to stick open or closed.

BC Code Requirements

BC Gas Code requires a sediment trap on all new gas appliance installations. The trap must be at least 3 inches long and located as close as practical to the appliance gas valve. Older installations may not have one — adding one during water heater replacement is recommended.

Maintenance

Sediment traps require no routine maintenance — debris naturally collects and stays in the trap. If you smell gas near the water heater or the gas valve fails prematurely, have a gas fitter check the sediment trap. A properly installed trap protects your gas valve investment.

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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.