dirt leg

I did a few inspections for a client about a year ago.

He was purchasing a home and was specifically looking for an All Electric House.

Heat Pump or Baseboard. No Natural Gas, Propane and/or Oil Heating was acceptable.

The requirement was due to the fact that He and his Family survived a Natural gas explosion in their home.

Cause of explosion was attributed to the lack of a sediment leg at the Laundry Dryer. Sediment lodged in the gas valve of the Laundry dryer allowing natural gas to leak at the completion of the Dryer Cycle. Leakage was ignited by the Water Heater.

Home exploded and was a total loss.

Client, Wife and 2 children survived.

He believed that Lightening could strike twice. He was not taking any chances.

Since then, I observe and report every instance where a Gas Sediment (Drip and/or Dirt) leg is not present.

Your mileage may vary…

I think he’s calling a sediment trap a dirt leg, which sound’s reasonable. Trouble is I don’t know what a sediment trap is. (See G2419.4 (408.4))

Well, if we were playing golf, I’d have you beat. Can one have a hole-in-zero in golf? :smiley:

Drip legs are for wet piping applications and Dirt legs are commonly referred to with Gas piping applications. Both however serve the same purpose.

In Massachusetts, Drip legs, Dirt pockets, Dirt legs (whichever you prefer to call it) are required when connecting to an appliance if the connection is made with black pipe. If the appliance is connected with soft copper, I look for a loop.

This leg serves as a collection point for moisture, and foreign particles (i.e. copper sulfide) that may be in the gas.

If there’s no leg present on a gas supply line serving an appliance, I write it up. Period.

Technically a “drip leg” is different from a “dirt leg”.

A “drip leg” is intended to catch moisture in gas, and is installed at all low points in a gas piping system for wet gas (IRC G2419.2).

A “dirt leg” (or more correctly a “sediment trap”) is installed at an appliance to catch tar, rust, scale, pipe dope, dust, debris, and other sediments. It is installed between the shutoff valve and control valve of a gas appliance, and is required by manufacturers and model codes for All gas fired water heaters, boilers, and furnaces (IRC G2419.4).

The terms “drip leg” and “dirt leg” are often interchanged, even by plumbers, but most of the time what you see at an appliance is the required “sediment trap” which is usually a “tee fitting with a capped nipple in the bottom opening of the run of the tee” (per IRC G2419.4).

Attached is a Press Release from the Gas Appliance Manufacturers Association (GAMA) concerning the often missed requirement for installing sediment traps.

JMO & 2 nickels … :wink:

To answer your original question, that seems okay as long as the dirt leg (aka “sediment trap”) is between the shutoff valve and the appliance control valve. Fouling of the control valve from sediment, and possible resulting gas leaks, is one of biggest reasons for the dirt leg being required for all gas fired water heaters, boilers, and furnaces.

Attached are photos of a typical gas fired water heater, with the dirt leg installed just before the control valve (and after the shutoff valve). If it’s not present, it gets a red flag every time for a plumber to come and install one … even though there are no problems with wet gas in my area.

The point of contention about dirt legs is usually not if they are required (they always are), but how long the leg below the tee needs to be. Some say 1" and some say 3" … I go with 1" minimum, and 3" desirable.

JMO and 2-nickels … :wink:



Speaking as a HVAC Service Tech for once I would love to see that sorry plumbers water heater buried behind the furnace in a closet. :frowning:

I hear ya , as I actually occasionally still work for my family HVAC company helping with installs and service. I have actually worked on servicing that furnace, and a little extra room would have been helpful. But the install essentially meets the minimum install requirements and it could be serviced … servicing was possible without too much trouble. But extra room would have been helpful.

Hence the common difference between what meets the code minimums and what is considered good practice.

JMO and 2-nickels … :wink: