Thread: Drip Legs

Can drip legs on gas lines be installed horizontally or vertically above the gas line? It was my understanding that they should be installed vertically UNDER the gas line to perform their intended job.

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IRC 2006 2419

As long as they haven't repealed the law of gravity, they need to point down as in Jerry's picture.

It is also important that the "T" is installed as shown in the picture. I see several with the side outlet pointing down and that is not correct.

From the IFGC Commentary-see pic
Bob

Jerry Mc's photo states:

Drip Leg
(Sediment Trap)

That is a "Sediment Trap", not a "Drip Leg".

A sediment trap is to be located there at the appliance, and configured as shown (as James said, with the tee down, not as shown in the photo Bob posted with the tee running across the down leg).

A "drip leg" is located at the lowest point in the line to collect condensation.

A "sediment trap" is to collect debris in the gas line, and can also collect condensation, but that (condensation drip leg aspect) is only effective for that one down turned leg of the gas line.

Bob H.,

In your photo, shouldn't the regulator vent also be pointing down, not up. That pipe with the 'U' on it can collect condensation and allow insects to enter/nest and cause a blockage, or is that not right (I know they make "vent protectors" for that use).

I've also seen some regulators with an arrow pointing "UP" cast into the housing, and those are not allowed to be installed on the horizontal, are they? (Not saying that regulator is one of those, in fact, it looks not to be one of them.)

This is a sediment trap I wrote up last week. Some of our better plumbers in Houston. Usually they dont put anything.

If you tip your head far enough to the left it starts to look good.

It might just be the angle that you took the photo, but it also looks like there is a kink in the flex connector right after the shut-off valve.

Sediment Trap - Drip Leg; direct from the UPC book. The only difference between a sediment and drip leg is location. Don't have time to post entire section from UPC explaining such.

Originally Posted by Jerry McCarthy

Sediment Trap - Drip Leg; ... The only difference between a sediment and drip leg is location.

Except that "sediment traps" are required at all appliances (a few exceptions such as 'illuminating' appliances and those where you 'know' they are, or are not, working), however, "drip legs" are only required where the gas has sufficient moisture in it to require them, and, yes, there is a big difference in their location.

It has been my observation that in a normal size house gas distribution system, the size of the system allows for the sediment leg at the gas valve to also serve as the drip leg for the system.

Originally Posted by James Duffin

It has been my observation that in a normal size house gas distribution system, the size of the system allows for the sediment leg at the gas valve to also serve as the drip leg for the system.

James,

Not quite sure what you are saying.

You used two different terms, was that intentional?

Are you saying that the sediment trap at the gas valve (meter is what I am assuming) serves as the only sediment trap required for the house?

Or are you saying that the sediment trap at the gas valve (meter is what I am assuming) serves as the drip leg for the house?

Sediment trap/drip leg I do not know if there is a difference. The purpose of the drip leg is to trap sediment before it reaches the gas valve or burner, not to collect or trap moisture. Natural gas has a large amount of moisture in it. For instance a 90+ gas furnace (condensing gas furnace) uses a condensation pump. The condensation comes from the gas itself.

Jerry, that home made vent protector is a function of the regulator mfr.--some models allow home made and some don't. Moreover, the orientation of regulators varies with models. Again, some must be oriented vertically only while others allow some variation. The overriding theme with regulators is to protect the vent from blockage or damage such as ice, debris, water, etc. Having said that, I find many vent screens blocked with lint, dirt, bubble gum, mud dauber wasps, etc. Regulators should not be placed in an area known to have snow drifts. It amazes me the utilities don't get the TV stations to remind everyone to shovel snow clear of their meter vents.

If you read the IFGC, it actually calls for capped tees upstream and downstream of MP regulators to allow attachment of a manometer (and to act as a sediment trap). There must also be a shutoff immediately upstream of these fittings to allow service of the reg. and attachment of the manometer on the tees.

I'm not sure I see proper support for the piping in this photo. It does have a ground union joint below the shutoff but the connections appear to be supporting the pipe itself. This strains the fittings. These pipes need to be painted for outdoor protection.

Trent, I'm not sure where you are getting the bit about a lot of moisture in NG. You can get a little water vapor trapped inside the open piping during installation and that's about it.
Bob

Originally Posted by Trent Tarter

Sediment trap/drip leg I do not know if there is a difference. The purpose of the drip leg is to trap sediment before it reaches the gas valve or burner, not to collect or trap moisture.

Incorrect.

The purpose of a "sediment trap" is to trap that sediment. That is why it is called a "sediment trap".

The purpose of a "drip leg" is, will, to collect "drips" from moisture which was within the gas and condensed inside the pipe on the pipe walls, which then runs down the pipe walls (inside the pipe) to the lowest point. That's why a "drip leg" is called a "drip leg".


DRIP.

The container placed at a low point in a system of piping to

collect condensate and from which the condensate is removable.

- G2419.2 (408.2) Drips.

Where wet gas exists, a drip shall be provided at any point in the line of pipe where condensate could collect. A drip shall also be provided at the outlet of the meter and shall be installed so as to constitute a trap wherein an accumulation of condensate will shut off the flow of gas before the condensate will run back into the meter.

- G2419.3 (408.3) Location of drips.Drips shall be provided with ready access to permit cleaning or emptying. A drip shall not be located where the condensate is subject to freezing.

- G2419.4 (408.4) Sediment trap. Where a sediment trap is not incorporated as part of the gas utilization equipment, a sediment trap shall be installed downstream of the equipment shutoff valve as close to the inlet of the equipment as practical. The sediment trap shall be either a tee fitting with a capped nipple in the bottom opening of the run of the tee or other device approved as an effective sediment trap. Illuminating appliances, ranges, clothes dryers and outdoor grills need not be so equipped.

Bob I stand corrected. Natural gas has a large amount of moisture in it before refining and distribution. The condensation from a condensing gas furnace comes from the flue gases being condensed and cooled.

After looking through some of the installation manuals from some of the gas furnaces and water heaters I have installed there seems to be no difference between a drip leg and a sediment trap.

The following is from a gas furnace installation manual.

A sediment trap (drip leg) must be used on both propane and natural gas
installations, to trap oil, condensate and other impurities, which might otherwise lodge in the gas, valve or plug the burner orifice. The sediment trap shall be installed as close to the furnace inlet as possible. When there is excessive condensation between the gas meter and the furnace, a sediment trap shall be provided at the outlet of the gas meter.

Where a drip leg is installed (close to the meter) the piping is pitched back to the drip. That leaves the smaller sediment trap for catching small amt.s of trash, thread cutting oil, hydrocarbon condensates, pipe dope, etc.

I've seen CSST installations where enough rain water entered the unsealed tubing during new construction that when connected, it formed a water trap. They had to replace all the piping. They tried blowing it out first but just as I told them, the corrugations held water which clogged a second gas valve. The trap would allow small amts. of gas to flow at lower rates so the pilot stayed lit. However, when the burner fired, the resulting flows caused turbulence in the trap so the flame was sputtering up and down.

Bob

The drip should also be installed as a trap, i.e., (from the code section I posted): "A drip shall also be provided at the outlet of the meter and ... " the next part is crucial " ... shall be installed so as to constitute a trap wherein an accumulation of condensate will shut off the flow of gas ... "