by Kevin O'Neill
Why do I see gas appliance installations that don't have a sediment trap? These traps, also called dirt pockets, drip legs, and dirt legs, protect the gas valve and regulator from rust, dirt, and scale that form on the inside of the gas line.
The International Fuel Gas Code states that ". . . a sediment trap shall be installed as close to the inlet of the equipment as practical. The sediment trap shall be either a tee fitting with a capped nipple in the bottom opening of the run of the tee, or other device approved as an effective sediment trap." This means that all gas furnaces, water heaters, boilers, unit heaters, and gas packs are required by code to have a sediment trap in the gas line ahead of the equipment.
Modern combination gas valves have as many as three valves and a regulator installed in a single compact package. Consider that these gas valves may be pilot-operated. In such valves, a small electric valve relieves the pressure on top of a rubber diaphragm, which then opens the main valve to allow gas to pass through.
There are many small passages inside the valve body. It only takes a small amount of rust to clog one of these tiny passages, causing a valve to malfunction.
If a crud-induced malfunction prevents a valve from opening, it may only cost you a service call. If, however, the gas valve fails to close, thats a much bigger problem. It could cause the unit to overheat and the heat exchanger to fail, and leave you with a potential liability.
It only costs a little bit of money to install a sediment trap on any gas burning equipment. That little bit of money buys you a lot of peace of mind. Protect yourself, protect your customers, protect your liability insurance, and protect your reputation. Make sure theres a sediment trap ahead of all gas-fired equipment that you install or service.
Kevin ONeill, CM, is the owner of ONeill-Bagwell Cooling & Heating, Myrtle Beach, SC. He has 27 years of experience in the HVAC service business and is a 20-year member of RSES. Kevin can be reached at 843/385-2220.