LPG supply line diameters

[Bob]

Hello,

My house is under construction and the plumber just installed the LPG gas lines. I am suspicious that he might not have this right.

I have a buried gas tank which is not yet connected to the house. It will be supplying a furnace, a cook-top, a fireplace and a tank-less water heater. The plumber split the input into two lines just outside the house with one line going to the water heater and the other line going to a manifold that splits off to the furnace, cook-top, and fireplace. These are all done with flex line (except the manifold and the pipes at entry to the house and to the water heater).

The cook-top specifies minimum 5/8 inch flex line supply and the plumber has used 3/4 inch from the manifold to the cook-top (about 30 feet). That's good, but he only has 1/2 inch from the tank to the manifold (about 15 feet). Seems like this is insufficient for the cook-top alone, much less the furnace and fireplace as well.

I plan on asking the plumber for details on how he established these line sizes and contacting the gas company to see if they will inspect the installation.

Am I seeing this correctly? Any suggestions?

Thanks, Bob

[Gary KW4Z]

First a disclaimer, I know nothing, myself, about LPG. That said, if it was me, besides asking in the Newsgroup, as you have done, I would contact the manufacturer of the equipment (furnace and cook top) as well as talking to a representative of the local Natural Gas company, if there is one. It's true Natural Gas and Propane does not use the same orifice size but given pressure of the gas and the fact it's gas I'm guessing that the delivery system (i.e. Size of pipes and procedure) would be the same. That way if there is any local codes you might gain knowledge about them also.

[Steve Barker LT]

I would be concerned at the use of so much flex pipe. Why not hard pipe for the long runs?

[Dan Deckert]

[Bob]

Dan,

Thanks for the links and info. I think I am OK with the buried tank. I wioll double-check but I believe the people who installed the tank are my propane suppliers. I did notice that the tank was backfilled with the same masonry sand used to put up the stonework on my house (as reccommended by one of those web pages). The tank is also situated in a way to meet all the guidelines on the other web page.

As I said, I plan on asking the LPG supplier to inspect the whole thing. If they won't do that perhaps they can recommend someone who will.

Bob

[Bob]

I will ask about that as well.

Bob

[Art]

You didn't say what pressure. Here we have 1/2 pound or 2 pound systems. For a 2 pound system those sizes are plenty big enough. For a 1/2 pound system I think the 1/2" to the manifold might ought to be 3/4". Ask the inspector what he thinks. Not just if it passes code but would he be okay with it in his house.

[Art]

Disregard the above answer. I read natural gas where you clearly said lpg. Sorry about that.

[Mike]

I know nothing about LPG but i think it may be like this. The tank is under pressure and the 1/2 line brings high pressure lpg to the manifold. The 3/4 line then distributes low pressure lpg to the appliaces. A small pipe at high pressure will yeild the same as a large pipe at low pressure.

[dpb]

Bob wrote: ... [snip more on LPG installation to the nub of the question]...

The other poster noting high vs low pressure distribution _probably_ has the right idea.

Where's the regulator installed? That's the key as that controls the high to low pressure transition point.

The LPG service company/supplier should, in fact, require that they inspect the installation before beginning service. Around here, anyway, that's part of the deal. If not included as a service, I'd ask for it and pay the service fee before going on. This should, of course, also include the leak/pressure test just as in a natural gas installation.

LP is no more hazardous than natural gas, but no less, either...both deserve respect.

[Bob]

Right - he may be on to something.

This I do not know right now. I can go check in a day or two. But, if the regulator is at the manifold it would mean that the installation is using flexpipe for high pressure and I don't think that is appropriate -- I think I remember the flexpipe had "5 psi" written on it. Would that be low pressure only?

LPG may be a little more hazardous. One difference is that it is heavier than air where NG is lighter than air. This was told to me by the guy who sells gas fireplace inserts. He said that is why LPG, but not NG, requires a pilot light by code -- so gas does not accumulate. I think the idea is that NG will tend to disperse but LPG will not.

Bob

[Steve Barker LT]

LP is more dangerous from the stand point that it is heavier than air. It will settle to low spots and go undetetected whereas natural will float around and be smelled.

[Bob]

In response to my own post -- I found out that (believe it or not!) the Texas Railroad Commission is responsible for inspecting LPG installations and the gas company won't deliver until there is a "passed" sticker from them.

What I don't know is if thie is just a "safety" inspection or if it will tel me if there is enough capacity to cover all my LPG needs.

Bob

[Raider Bill]

I just installed a LPG vent free fireplace insert at my house. Destructions called for 5/8 supply line which really didn't make mush sense as it connects to a 3/8 flare fitting on the appliance. Not much more than a 1/4 opening in the 3/8th flare. Works great though, getting me through these hard cold florida winters.

[Art]

Be there for the inspection and ask questions. Specifically "Was it done right?" or "Would you be okay with this in your house?". Most inspectors I have met are nice guys that don't mind telling you what they think. Passing code and having a good job are two different things and every inspector knows that.

[Bob]

I got a guy from the gas company to take a look. My worries were mostly due to my own ignorance about how LPG installations work.

My 1/2 inch supply line os OK since it is in the "high pressure" (2 PSI) section. This will get reduced to 6-8 ounces at the manifold with a regulator; thus the smaller line (at high pressure) can adequately supply the multiple lines leaving the manifold (at low pressure).

At entry to the house there will be a regulator reducing the pressure from

10 PSI to 2 PSI (to feed the manifold) and another regulator to get low pressure to the hot water heater. The tank itself will have a regulator to supply 10 PSI to the house.

The guy from the gas company did say he would do things a little differently: He wouldn't split off the hot water heater at entry to the house but instead run a line from the manifold back to the water heater, eliminating the need for one of the regulators.

Bob