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Not reducing gas line after it branches off from the main to appliances and furnace

So I'm about to redo the gas pipes from my heater and water heater and add a line for the gas stove and my uncle was telling me that we should run the 1 inch for the branches to the apliances and other things and at the very end just make the reduction to 1/2 valve for the apliances. My thing is does it lose pressure because it's not being reduced from the main line all the way to the apliances? We live in texas and a friend that's a plumber told my uncle we could because it wont be traveling that far, anyone know I'f hes wrong?


  • Zman
    Zman Member Posts: 6,793
    You will need to post some more info to get to where you are going.
    The type of fuel, BTU rating of the appliances and distances would be a good start.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Steamhead
    Steamhead Member Posts: 14,771
    We usually run gas piping full size to the last takeoff. This keeps the pressure drop down.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Jamie Hall
    Jamie Hall Member Posts: 16,617
    Simple answer to your question on will it lose pressure because of the larger size? No. As @Steamhead said, if anything it will reduce the pressure drop, which translates to the pressure at the appliance being nearer the pressure at the meter.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • There are sizing tables for this purpose. If you use these tables to pipe your appliances, you will have a system that will deliver the calculated amount of gas at a minimum pressure drop. Natural gas will size differently than propane.

    You start at the meter with a pipe large enough to supply all the appliances, even though they are almost never on at the same time, but sometimes they are. As you make drops to the appliances, the pipe size reduces. There is no need to keep the pipe size larger than needed unless you have future plans to add gas equipment. But to answer your question and like Jamie said, the larger pipe won't effect pressure drop.

    Make sure you install drip legs when you go vertical to the appliances. Some appliance manufacturers will void the warranty if you don't.
    Often wrong, never in doubt.
  • monsterking94
    monsterking94 Member Posts: 3
    Hey sorry I haven't responded back I've been working, but we have bought the apliances for the house but it's going to be a water heater, gas fire place, gas heater, stove and dryer. So from the meter to the house is I believe 20 ft and in the inside it goes up 8 ft and branches to the dryer, and then goes across the attic 10 ft and drops into the water heater and gas heater. From there it goes 10 ft left and 7 feet down and 6 ft across. And then lastly it goes 15 ft across the house to the fire place but the fires place is reduced to 1/2 inch from the main line so its 15 ft of 1/2 inch. So my question is do I have to reduce it from the main line to the apliances or can I just run 1 inch and add a 6 inch reduction to 1/2 for the apliances or will that be too big? Sorry for the confusion I'm not really good at describing all of this, thanks for the help in advance!
  • monsterking94
    monsterking94 Member Posts: 3
    Ok thanks that's what I was worried about the reason we are using 1 inch pipe is because a friend of ours has a lot left over and my uncle wanted to use them since they were free and we will be using drip legs on them as well thanks everyone!
  • Zman
    Zman Member Posts: 6,793
    There is no issue with running oversized gas lines. Without BTU ratings, it is impossible to tell if 1" is undersized or oversized for your application.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • That's just a silly reason to use oversized pipe. The stuff is dirt cheap. Throw away what you don't use or give it away to someone that regularly works with it. Or take it to the scrap yard and you'll get 1¢/pound. More than anything, 1" pipe is harder to work with than smaller pipe, the fittings are more expensive, your measurements have to more exacting to fit it into joist and stud bays and (to me), it won't look professional because I've never seen it done that way.
    I'm not saying your Texas plumber friend is wrong as he confirmed what everyone else is saying, that larger pipe won't affect pressure drop.
    Often wrong, never in doubt.
  • Leonard
    Leonard Member Posts: 903
    edited September 2018
    On the flip side oversized lines are nice since might allow you to add another gas load (appliance) in future without adding new pipes.

    Look at pipe pressure drop flow tables to see if larger dia pipe is buying you any SIGNIFICANT extra flow capacity, to see if it's worth extra fitting costs and labor.

    I use a machinist's rule (1/32 and .01 inch increments) to accurately measure things like how much of pipe thread distance disappears into threaded fittings like Tee and Elbows. Likely overkill for pipes, but I'm an engineer and routinely design machines to similar or better accuracy