PVC pipe on gas regulator?

[Randall Clark]

On the exterior of the home next to the back-up generator (propane powered). This PVC pipe ran under the deck and was capped off. What is this port for on the regulator?

[Bob Harper]

You can use special PVC that is listed under UL 651 as PVC above ground conduit or flexible liquid tight NM conduit listed to UL 1660 with fittings listed to UL 514B.

The termination cannot be 'capped'. Be sure it is not a screen. Regardless, it must be positioned and protected from ice, rain and bugs and be located at least 10 ft from any source of ignition.

[Jerry Peck]

Bob,

Question for you one venting regulators like that: With LP being heavier than air, and NG being lighter than air, are there limitations on 'trapping' the regulator vent piping, and, should the vent piping slope up for NG and down for LP or does it not matter enough to matter?

Okay, so that is more than just one question ... ;)

Thank you,

[Bob Harper]

You know Jerry, I had the same question so I reviewd '58, 2011 rev. and could not find anything. It does make sense to vent LP downhill all the way with no trapping. It will flow past if the diaphragm blows but it will hold some in that trap once the gas flow is stopped.

That termination has to be capable of handling a 10 psi discharge.

[Jerry Peck]

You know Jerry, I had the same question so I reviewd '58, 2011 rev. and could not find anything. It does make sense to vent LP downhill all the way with no trapping. It will flow past if the diaphragm blows but it will hold some in that trap once the gas flow is stopped.

That termination has to be capable of handling a 10 psi discharge.

Bob,

Thank you - sometimes my logic seems to either not make a difference or maybe it simply has not been addressed, such as heavier-than-air LP sinking downward and lighter-than-air NG rising upward ... :)

Glad to hear you were questioning it too. :cool:

To me, it just makes sense not to provide a trap which could remain filled with gas after the gas has been turned off. Granted, with the gas still on, the discharging gas should flow toward the open end of the vent line, but, like a garden hose, when the water is turned off, the hose is still full of water, and the gas line is still holding gas. Could be that I just over-think some things. ;)

[John Kogel]

Could be that I just over-think some things. :D:confused::D
Maybe not this time. I would call that out as well. If the regulator is too close to a flame source or too low, then you move the regulator.
That trap could fill with rain water or you could get mud daubers building a nest in there.

[Bob Harper]

The vent tube allows a regulator to remain too close to an ignition source but move the vent discharge point at least 10 ft. from an ignition source. Sometimes, they'll run liquidtite all the way to the bonnet of a buried tank.