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    Gas Pipe Sizing (16 Posts)

  • Oski Oski @ 2:12 PM
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    Gas Pipe Sizing

    I have a gas pipe sizing question to which I have been unable to get a satisfactory answer. I would like to replace my current water heater with a tankless one. Because of the increase in BTUs, I understand that it will be necessary to increase the main gas pipe from 3/4"  to 1¼" .  The pipe coming out of the meter, however, is 3/4".   I have read that it is not permissible or effective to go from a small gas pipe to a larger one. Nonetheless, the plumbers I have talked to have not explained how or why this permissible when connecting to the pipe coming directly out of the meter. Any help clarifying this issue would be appreciated. Thank you.
  • Tim McElwain Tim McElwain @ 3:42 PM
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    The outlet of the meter

    bar is called the point of delivery. The utility is required to provide a certain gas pressure at that point typically on high pressure regulated gas services it is 7" Water Column pressure roughly 1/4 of a pound of pressure coming out of the regulator. On low pressure systems it could from 7 to 10 " W.C.. The tables and charts from the Fuel Gas Code  that are then used to determine pipe size along with an allowable pressure loss will determine the size line required for the length of run and the 'BTU requirement of the equipment. The 3/4" outlet from the meter is then negated by the increase in size of piping to the equipment. The main concern is to have the same gas pressure at the meter and have no drop in gas pressure to the farthest appliance on the system.
  • j a j a @ 4:13 PM
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    Hello   It is the installers responsibility to make sure you have enough gas available to support your new load...He will call the local gas company and find out what is coming into the property and how long that run is...Often the engineering part if the gas supplier will do a work sheet based on the info your fitter gives you...If your size or pressure is incorrect do not install the added appliance, until it is...It will not work as required...Gas company installs up to the meter bar...
    From there your fitter takes over with doing the inside fit.. He can use a couple of different sizing methods based on his design procedure..Often years back we over sized in low pressure areas....If you have a regulator before your meter you are in a high pressure area...that is good....Don't know the make or model of what you are installing but they normally spec out around 185 k at peak load...Tell us what you have for gas appliances and we can give you what size the gas pipe should be at the outlet of the meter....The more info the better....Hope this helped
  • Oski Oski @ 6:26 PM
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    Additional Info

    The regulator is before the meter, so I must be in a high-pressure area. The gas appliances on the system are as follows:

    Trane XE 78 Furnace                                              -60,000 BTU
     LG Gas Range  LRG3095ST                                -69,000 BTU     
    Rheem Eco-180 DVN Tankless Water Heater    -180,000 BTU
    Kenmore Gas Dryer    Model 110 79812990      - 22,000 BTU
                            TOTAL - 331K BTU

    The spacing of the appliances is as follows:

    Meter — 30'— Furnace — 10' — Range — 30' — Water Heater — 10 — Dryer

    Your help and advice is appreciated.
  • Tim McElwain Tim McElwain @ 9:05 PM
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    First things First

    we do not use 3/8" pipe anymore.

    As too sizing first of all the meter needs to be sized correctly for the 331,000 BTU's for your system typically a meter that will handle 400 cubic feet per hour.

    Using the longest run method on Schedule 40 pipe inlet pressure less than 2psi at an allowable pressure loss of 0.3" W.C. I would run 1 1/4" pipe all the way to the tank-less water heater simply because of the way those units operate. Then 3/4" of the 1 1/4" to the range and finally 1/2" to the dryer.
  • j a j a @ 7:30 PM
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    Based on the info as I interrupt it ,your first size  manifold off the meter will be 1 1/4....If you were to use the home run method its a 1 inch to the water htr  1/2 in to water htr and range and 3/8 in to dryer....This is not to be used as the exact answer as I will leave that to your installer...Sizing,, once all is measured, takes approx less than one minute to figure out...Work backward it becomes simple.  j a
  • SWEI SWEI @ 12:49 AM
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    sizing rules

    Are different for the utility, so what really matters is the CFH capacity of the meter.  It's quite common for a meter to have an exit pipe which is significantly smaller than the building main (mostly because they're so short, especially in comparison with the distribution system length.)
  • j a j a @ 7:34 PM
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    12  inch to furnace not water heater   Sorry
  • j a j a @ 7:34 PM
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    12  inch to furnace not water heater   Sorry
  • j a j a @ 7:59 AM
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    Using 30 ft, if that's your longest run, a one inch black pipe will handle 285 k that would be over sized by 1/3...I install, service and repair these units...That's big enough....A properly sized system will work fine every time..As   far as 3/8 I really have never used it, however its in my code book and they do sell it, at my supply house,,I  don't use csst but I do see it is listed on there sales sheet...That said I would think someone uses it,,that is why I sized it that way..I have no idea where you live...Trust your plumber, as long as he is licensed and files all the proper permits...j a
  • Oski Oski @ 10:56 AM
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    Thanks for all the help.  If I understand things, it will not be a problem to transition  from 3/4" pipe to 1 1/4 " at the meter provided that the proper pressure is maintained throughout the system.
  • Henry Henry @ 5:16 PM
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    Gas pipe sizing

    It is NOT for the consummer to be involved with gas pipe sizing! It is the responsability of the licensed gas piping and appliance installer to provide the proper gas pipe sizing. ANY inference without having an actual site visit is supposition as in court inadmissible! If you did not see the existant and the new, how can can you advise??? As professonls in the field, we are NOT doing a responsible service by suposition!
  • ChrisJ ChrisJ @ 4:39 PM
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    As a homeowner in the state of New Jersey I ran every inch of fuel line in my own home with a permit.  The fuel line was pressure tested by my self and inspected by a state inspector.  My installation passed inspection way back in the fall of 2011.  The fuel line had to pass inspection before the NG company would unlock the meter. Luckily in my case was never locked as they installed it after my inspection.

    Of course I researched code in my area and bounced some ideas off of others in the forum while I was doing it.  In my opinion there is absolutely nothing wrong with that. 

    I would also like to point out, all of my piping was installed tight with Megaloc pipe compound and supported appropriately.  However the guy who installed our $1000 gas dryer felt it was not necessary to use any thread sealant on the NPT threads where his flex hose connected to the line I installed.  I of course disconnected it and reinstalled it properly.  Just to be clear, these were NPT threads NOT a flare connection.

    When I did mine I was told I could use whatever size I wanted it would just have to be adapted to the meter's 1" outlet.

    That being said, if I was doing it I would go with what Tim recommended. 
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    This post was edited by an admin on May 29, 2012 4:53 PM.
  • meplumber meplumber @ 6:27 PM
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    ChrisJ that isn't the case in every jurisdiction.

    While most people can do whatever they want to their own home with proper permits, gas work is typically not one of them. In most jurisdictions, the gas provider will require that any interior work be performed by a licensed and insured contractor. Why? To shift liability should there be a problem. I would say that your situation was the exception and not the rule.
  • ChrisJ ChrisJ @ 7:21 PM
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    Probably true

    I will admit I was surprised when they told me I was allowed to do it with a permit. I was also surprised I was allowed to install my own steam boiler.

    I love where I live. :)

    But at the same time, we cannot assume that it is not permitted where Oski is. Perhaps it is. Maybe he is simply trying to educate him self so he knows what is happening.
    Weil-McLain EG-45 connected to 392sqft of radiation via two 2" risers into a 3" drop header and 2" equalizer. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures updated 6/5/14.
    This post was edited by an admin on May 29, 2012 7:22 PM.
  • j a j a @ 6:58 AM
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    heating help

    Henry  This site is called heating help..And that is what I believe, most people use it for..If we can help guide the homeowner, in the right direction,and tool him with good questions, to ask his installers then we have HELPED...Goggle gas pipe sizing some day, its out there....It really is no big secret.....Go by your local codes, and you will be safe, that is what they are in place for....Codes are not just codes they are the law, at least they are here in my state/country.....Heck we even install 3/8    JA
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