new LP gas line sizing question

[srossman]

Hi everyone, I was hoping someone could shed some light on a question that I have. I'm in the process of putting gas lines in my house and am trying to figure out the proper size to buy. For right now, I installing a tankless water heater which requires a 3/4" line. In the future I will also be installing a gas cooktop and if the electric furnace ever goes, I'll put in a new gas furnace also. I want to get everyting plumbed out now, so that when I am ready for the stove, it will be easy to hook into the line. Right now the run from the tank to the water heater is about 18 ft if that matters.

Thanks for all replies,
Scot

 

[gordon21]

Doesn't the local gas company do all that plumbing for free???

 

[Dusty]

I ran 1/2" soft copper tubing for my dryer and gas stove. Gas dealer said that 1/2" would have been enough, unless there was a lot of demand all at once.

 

[AndyM]

Doesn't the local gas company do all that plumbing for free???

Not up here, for natural gas or LP!
In fact, the local natural gas company only owns the lines at the road. If someday happens from the road to the house, it's on my dime! To make things worse, the gas line ended 400 feet down the road from my property, so I had to pay the gas company to run it up the road to my lot.

I've always seen the plumbers around here install black pipe instead of copper, at least in this area.
I've got a one inch main line from the gas meter on the side of the house, running the length of the basement across to the other side of the house.
There are half inch lines running off the main line to my furnace, water heater, and gas fireplace, along with capped off tees pointing toward the front and rear of the house for future expansion and one each under the stove and clothes dryer in case we switch from electric someday.

 

[Dusty]

Black iron is always used with Natural Gas, but soft copper seems to be the standard with LP (propane). I used black iron in the garage for my heater, since it is subject to damage out there.
Dusty

 

[AndyM]

Black iron is always used with Natural Gas, but soft copper seems to be the standard with LP (propane). I used black iron in the garage for my heater, since it is subject to damage out there.
Dusty

At our last house, I had paid someone to run a natural gas line underground from the house to the unattached garage. That plumber wanted to use copper, but I was a little leary since I had never seen copper used in this area for natural gas. I still haven't since that time either.

 

[montejw]

Hi everyone, I was hoping someone could shed some light on a question that I have. I'm in the process of putting gas lines in my house and am trying to figure out the proper size to buy. For right now, I installing a tankless water heater which requires a 3/4" line. In the future I will also be installing a gas cooktop and if the electric furnace ever goes, I'll put in a new gas furnace also. I want to get everyting plumbed out now, so that when I am ready for the stove, it will be easy to hook into the line. Right now the run from the tank to the water heater is about 18 ft if that matters.

Thanks for all replies,
Scot

I used to know how to do this, but haven't used it for about 5 years now, so now I use Google. metrokc.gov/health/plumbing/gaspiping.htm has some good information. I searched for ["natural gas" pipe sizing], leave off the square brackets, there are lots of places to find this stuff. That page had a lot of good information, sizing the main run as well as the branches.

I'm assuming natural gas and the meter just outside the house. In the couple years I did gas piping we didn't run many house supply lines over 1" nominal pipe size. You could run bigger into the house and be okay, just pay more for the pipe.

Doh! I just noticed the "LP" in the thread title. Maybe search for [propane pipe sizing]. I think you could use natural gas pipe size and be okay, if I remember right LP runs at a little higher pressure making the pipe sized for natural gas a little bigger than it needs to be.

Monte

 

[jloppy]

Once you find a pipe sizing table, be sure you're using the right one for the least amount of pressure drop ( a 1" WC-water column) drop is about average. Copper tubing is approved for gas piping under UL, AGA, ANSI, etc whether it's propane or nat gas.

LP runs @ 11" wc press and nat is 7.0" wcp.

Black malleable steel will carry more BTUs than tubing with a low press system. Most folks are getting lazy, running tubing all over the place, setting the house piping on 2lbs, and putiing step down regulators at every appliance. I'm not crazy about this idea...it's safe, but...well, this is your decision.

Bigger pipe now is easier than later.

my $.02

P.S. Soap all those fittings!!!!!

 

[johnk]

Natural Gas with copper lines have to have flare fittings in case bumped into they won't pull apart. Copper actually oxidizes with nat. gas and has the potential to plug pilots after time. The orfice in a Nat Gas orfice is an 80 drill which is smaller than a bristle on a wire brush which isn't much. The size of the pipe has to do with BTU's and length of the run if this is any help..

 

[kmdigital]

Copper actually oxidizes with nat. gas and has the potential to plug pilots after time.

Supposedly, this isn't true anymore according to the gas companies. The gas is cleaned now, so there isn't a problem using copper anymore.

As for sizing for LP gas, it depends if it is inside the house or outside from the tank to the house. Usually, there is an "A" or high pressure regulator at the tank which reduces the pressure to 10 PSI, and then a "B" or low pressure regulator which reduces it to around 10" - 11" WC inside the house. Obviously, the line can be much smaller at 10 psi then at the 10" WC to carry the same amount of gas.

To size the low pressure line you need to know several things. First, how long the pipe is from the regulator to the farthest destination and second, how many BTUs are required by all the appliances on this line. Generally you figure about 1" WC pressure drop with all appliances firing at the same time, and then use the table to determine what size pipe to use. The pipe can be quite a bit smaller for LP then for natural gas because the pressure is higher and the BTU content per cubic foot is greater.