Sediment traps might have more slang terms than any other component in a home; Drip, Drip Leg, Drip Tee, Drip Elbow, Sediment Tee, Dirt Tee, Dirt Leg, Dirt Pocket, Drip Pocket.... you get my point. These names all refer to a short length of pipe installed on the gas piping to an appliance that is designed to catch any foreign debris in the gas line, and prevent it from getting in to your fuel burning appliance and gunking things up.
The basic requirements. Sediment trap requirements are fairly consistent across the country, but Minnesota is a little more strict. Minnesota requires the following for a sediment trap:
- Must be installed as close to the inlet of the equipment as practical
- Must be installed ahead of all pounds-to-inches pressure regulators
- Must be made of a tee fitting with a capped nipple, a minimum of 3 inches in length, in the bottom opening of the run of the tee
- Provide a 90-degree change of direction of gas flow (the photo at right is an improper installation, because it does not provide this)
- The cap shall be at an elevation lower than the tee fitting.
Minnesota requires sediment traps at all automatically controlled gas utilization equipment, but good luck getting a straight definition of what "automatically controlled" is. I've been trying for the past four years, and I've received different answers from different authorities. Some jurisdictions say that any appliance that automatically controls the flow of gas is automatically controlled, such as a clothes dryer or a range. Other jurisdictions say that only appliances that turn on and off by themselves are automatically controlled, such as a furnace and water heater. That's the definition I prefer to use.
How important are they? That's debatable. While a missing sediment trap is certainly a code violation, I don't feel that this is a serious defect. It's just a good sign that an amateur has been doing work on the house. I've taken apart many old sediment traps just out of curiosity, and can you guess what I've found at the bottom of every trap? Click the photo below to see.
They're becoming a thing of the past. Natural gas is actually a very clean product today, and I've never found a trace of sediment at the bottom of any trap. The national codes for gas piping don't require sediment traps at illuminating appliances, ranges, clothes dryers, or outdoor grills. This leaves furnaces, boilers, and water heaters.
But if you live in Minneapolis... you better have your sediment traps installed. For a Minneapolis Truth-In-Sale of Housing Evaluation, any appliance that is less than three years old (from the date of the evaluation) must have a properly installed sediment trap. If it doesn't, this requires repair with a plumbing permit.
Reuben Saltzman, Structure Tech Home Inspections