Gas line - drip leg


Old 12-07-03, 05:20 PM
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Gas line - drip leg

installing new furnace. connecting gas lines

q1) what is the purpose of a drip leg?

q2) how long should it be?

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Old 12-07-03, 05:44 PM
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Drip leg is a tee configuration at the point of last turn into appliance it serves.

It serves the purpose as a low point for dirt and debris to collect.

Usually a couple inches most times with a cap.

In my area they don't require this but it is still installed since it was code for so many years.

I am sure the gas is clean, but that doesn't mean that old piping systems don't have dirt that travel around in them.
Old 12-07-03, 06:51 PM
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Drip legs used to be important when gas hat a significant water vapor content., The water could condense out as droplets, or cause corrosion and scaling in the pipes. Since gas is now sold by the ?therm?, moisture directly decreases the available heat from the gas and has been pretty much eliminated. He drip leg still can catch any debris in the lines that can jam a gas valve and they are cheap insurance. Even if your line is new, the condition of the distribution system is often unknown.
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