Author Topic: Underground gas line installions and relief lines  (Read 865 times)

Offline slo-115

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Underground gas line installions and relief lines
« on: October 16, 2016, 01:37:12 PM »
I've had a bit of a time pricing out propane generators and pool heater installs. My biggest issue is with local propane suppliers, and the way they go about their installs. I always run low pressure propane (11"wc) underground though 1" approved plastic pipe, with 2 risers (super expensive). This way i have no issues in clearances as the tank is always 10ft or more away from the appliance. My issues is the propane company will always beat my install price. They run high pressure (10 psi) underground in 1/2" copper to the appliance. Then mount the secondary reg to the appliance, followed by venting the regulator underground (using gas tite) 10ft away from the unit. I know the csst isnt approved for underground use, even though its only being used as a vent. The way in which the reg is vented, moisture will get trapped in the vent line causing a potential ice blockage. Some homeowners think im mental, as my price is far more then the propane supplier, but i maintain my stance. Can anyone shed some light on this?

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Re: Underground gas line installions
« Reply #1 on: October 16, 2016, 02:24:31 PM »
I would normally use a high pressure underground gas line and install a secondary regulator at the house.

Gastite CSST can be buried underground.  The Gastite CSST Guide Section 4.9 says,

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4.9 Underground Installations
a) Gastite®/FlashShieldTM CSST shall not be buried directly in the ground or directly embedded in concrete (e.g. slab on grade construction, patio slabs, foundations and walkways). When it is necessary to bury or embed Gastite®/FlashShieldTM CSST, the tubing shall be routed inside a non-metallic, watertight conduit that has an inside diameter at least 1/2 inch larger than the O.D. of the tubing (Fig. 4-94). For ends of the conduit installed outdoors, the conduit shall be sealed at any exposed end to prevent water from entering.

I always prefer to use Schedule 40 steel pipe for my relief vent lines above ground.  Be careful if you use copper that it is sized properly.  I have seen propane distributors use Clause 5.7.3 of the B149.2-10 or Clauses 5.5.4 and 5.5.7 of the B149.1-10 to red tag undersized relief lines,

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Clause 5.7.3 - A line relief valve assembly, including its connections, shall be of sufficient size to provide the rate of flow required for the system to which it is connected.

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Clause 5.5.4 - Except as specified in Clause 5.5.5, when a pressure regulator with internal relief or a gas overpressure
relief valve is installed, it shall be vented separately to a safe location outdoors by a vent line
(a) of steel pipe, or of seamless steel tubing or copper tubing that complies with Clause 6.2; and
(b) of a size
(i) at least equal to the nominal pipe size of the vent outlet of the valve or regulator increased as specified by the manufacturer’s instructions; or
(ii) in the absence of manufacturer’s instructions, increased by one pipe size diameter for every 50 ft
(15 m) or part thereof that the vent line extends beyond the initial 50 ft (15 m). This increase shall be made at the connection on the device.

Clause 5.5.7 - A vent line shall be of sufficient size and configuration to prevent impedance upon a regulator.

Their issue is using 3/4" copper would cause an impedance upon the regulator, as the inside diameter of 3/4" copper is not equal to 3/4", which is the size of the relief opening.  The vent line would have to be 7/8" copper.  The Gastite 3/4" CSST has a nominal diameter of .75 so it would be okay to use.  Some CSST manufacturers require their fittings be wrapped with silicone tape when installed outdoors.  Gastite does not have this requirement.  As long as they are using a conduit for the buried CSST and installing a screened termination, there should be no problems.

I have wondered about the trap that seems to exist when we exit a regulator relief, from the bottom, then snorkel up and over, but there are no Codes preventing that and I have never seen a relief line frozen with ice.