Sediment traps have been required on gas piping systems for many years, but there is a lot of confusion about them. Read on to learn what they really are, where to install them, and how to configure them properly.

Sediment Trap vs. Drip Leg

“Drip leg” and “sediment trap” are often used interchangeably, but they are really two different things. Drip legs (technically call just a “drip”) are installed to collect condensation in a gas piping system, so they are installed in a low point to prevent condensation from running back into the gas meter. Wondering why you have never seen one of these? They are not required where the local gas utility provides “dry gas” – which is defined as “a gas having a moisture and hydrocarbon dew point below any normal temperature to which the gas piping is exposed.”

On the other hand, sediments traps are installed to collect sediment, rust, or debris in a gas piping system that can clog a gas appliance burner and cause a malfunction.

Which Appliances

According to the 2016 California Plumbing Code (CPC), sediment traps are required for all gas appliances except: illuminating appliances, ranges, clothes dryers, decorative appliances for installation in vented fireplaces, gas fireplaces, and outdoor grills. Those are quite a few exceptions. Most homes need to have sediments traps installed on the gas piping supplying water heaters and furnaces.

Where to Install

This section of the plumbing code has been changing in the last few code cycles, creating some confusion. For a while, sediment traps were required “as close as practical” to the appliance, which lead many installers to put the sediment trap after the flexible gas connector. The 2016 CPC clarified that the trap should be installed after the appliance shutoff valve, but before the flex connector. Presumably, this is to facilitate cleaning the trap.

How to Configure

According to the CPC, a sediment trap “shall be either a tee fitting with a capped nipple in the bottom outlet, as illustrated in Figure 1212.8, or other device recognized as an effective sediment trap.” It’s important to note that Figure 1212.8 shows the gas coming in the top inlet, not a side inlet of the tee fitting. When running gas piping for a new appliance, installers should run the piping high enough that it can run down to the sediment trap – to avoid potential complications. An internet search did not reveal any proprietary devices, so it looks like installers will be making their own for the time being.