Running propane piping


Senior User
I am still spending more time on home projects than woodworking but I believe it is winding down. I reframed and finished a set of stairs, refinished another set, replaced all the molding in the house, installed new kitchen and bath cabinets and appliances, etc.. In February I paid a local propane supplier to set a 100 gallon tank and install a tankless hot water heater. My old electric was in bad shape. My house was totally electric when I bought it and I didn't love being without anything in the rare event that there was an interruption. So I got the tankless and a big propane tank.

My plan was to install an insert that can supply heat in the brick fireplace and to feed the Weber grill on the back porch form the big tank. That meant running a propane line almost the length of the house. I ended up buying 80 feed of soft copper and a little black iron. The iron is in the inside wall of the house - where a screw or nail could hit it - and the soft copper runs in the crawl space. In putting this in I made iron pipe joints (in that piping but a lot of brass fittings have this style connection too), soldered joints, and flared joints.

I learned, the hard way, that brass fittings for flared joints are sold by the OD of the pipe, not the ID. McMaster Carr is good and is clear, but I wanted fittings they did not have and the other place I used, Propane Warehouse, was not clear. But that got sorted. I also learned that my Weber grill has 3/8 flare connections for the gas supply. Grills have a regulator to drop the pressure of the tank to the low pressure the grill needs. But big propane tanks have that so the pressure in the lines is about 1 psi. Weber wants a lot of money for a line to use on their grill (I think they said $50 minimum) but once I knew the size, I got a nice stainless braid line for $30 from Amazon.

I also learned that flared connections, at least in 1/2 ID, 5/8 OD pipe take significant pressure to close. About half of mine leaked a little until I tightened them some more. In some cases, the piping was not perfectly aligned. But with more pressure they sealed. Except for one where I was connecting black iron pipe to soft copper and the black iron was at a bad angle. I ended up taking that out and running another 7 feet of soft copper so I could connect to the black iron properly. Getting the iron pipe through the wall into the crawl space was not fun and resulted in the angles that caused piping problems.

I did not plan to put in soldered connections but I didn't have all the fittings I needed and was tired of ordering more. I also twisted the soft copper pulling it through a hole in a floor joist and needed to cut out the bad part. But I have soldered a lot of water lines that operate at considerable higher pressure and thought it would be fine and it is. None of my soldered connections leaked. None of my pipe fitting connections leak either. I used both teflon tape and pipe dope on those and tightened them pretty well.

Soft copper is fairly easy to bend but it isn't totally easy to work with when it is in a coil under the house and you need it to be straight and go over wires, plumbing and duct work. When you bend it, it often is not then exactly round. That messes up getting the nuts for flare connection on and soldered connections made. I figured out that if I put the clamp portion of the flare tool on the pipe where I needed to round it, the pipe would round up nicely.

Another small tip is that the valves they sell for fireplaces are threaded for iron pipe so you can move the valve down (in my case below the closed cell insulation on the under side of the floor) and still have the key guided to the valve (by the iron pipe).

I did not find great you tubes or other on line resources. I guess most people hire a plumber. But it wasn't a bad job except that the work was mostly in the crawl space. I do not have much headroom in mine. So anything becomes more difficult.


Corporate Member
And, here's a vote for installing lights in the crawl space. Switch is just above the crawl space door.


For some reason, I don't think soldiered joints are permitted on gas lines. It's been a lot of years since I ran gas lines, so I may be wrong. Back then everything was in black pipe once it entered the structure. As for flare fiting, you have to use the thick nuts made for gas lines.


Senior User

Thanks, I think you have a point. I thought about pressure and soft solder joints are clearly OK from that standpoint. But there is a concern with the solder joints leaking in a fire and that causing the gas to come out making the fire much worse. Silver solder is apparently allowed but not soft tin or lead based solder. I may need to buy some more flare fittings. While I do not love them, they apparently meet all requirements. I was short of flare fittings and just used what I had without checking.

The nuts I used on the flare fittings were heavy brass ones meant for propane fittings. I was surprised how much pressure I could put on them (when I had a joint that was leaking a little).


Our Sponsors