Sediment traps on gas lines: what and why as part of a home inspection
Have you ever noticed that extra little leg of gas piping running to your furnace or water heater and wondered what the heck happened? It’s called a sediment trap.
Sediment traps are intentionally installed to help prevent sediment in the gas piping from getting into the gas valve or burner area of an appliance and fouling things up. The photo below shows eighteen years of sediment accumulation at the first sediment trap at my own house, which is located on the main gas line just before the pressure regulator.
I’ve taken apart many sediment traps out of curiosity, and this was the first one where I’ve actually found anything. The sediment traps at my furnace and water heater were completely empty. Sediment traps have been required for approximately forever, and they’re still required today.
Side note: old-school guys and girls call them “drip tees”, “drip legs”, “dirt legs”, and several other names that you won’t find in the current code. While the old code language only required sediment traps where the gas piping dropped down to appliances, there is no longer such language in the code. Sediment traps are required at all automatically controlled gas appliances.
In other words, sediments traps are required at furnaces, boilers, water heaters, clothes dryers, ovens, space heaters, unit heaters, gas fireplaces, and more. Despite these requirements, I personally can’t recall ever seeing one installed at a gas fireplace, they’re almost never installed at ovens, and just yesterday I inspected a new construction home with a clothes dryer in the basement that was missing a sediment trap on the gas line. It seems that installers and municipal inspectors don’t care much about the presence or absence of sediment trap.