Gas piping routing options & best meter location

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by makemenuconfig, Mar 18, 2021.

  1. makemenuconfig

    makemenuconfig New Member

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    Jun 6, 2019
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    Seattle Area
    Hey guys,
    I'm working on an addition and need to relocate the gas meter and have the house repiped to accommodate the larger load. I wanted to see what you all thought about which location is going to make more sense since I need to set this up with the gas co. soon.

    I want to include a NG. backup generator since I have a sewer pump that needs to keep running when the power goes out. At max output, that load is 250k btu/h. The rest of the loads in the house total 480k btu/h, about half of which is a tankless. I am including all possible fixtures I'd like to have installed since the gas company needs that for sizing the meter even if a few don't end up happening.

    My initial reaction was to locate the meter at the front center of the house (shown option A) since it is close to many of the fixtures. Using longest length method, I figure I need to have a 2" main installed up the wall, through the attic, and into the mechanical room. There the furnace, fireplace, outdoor, range drop off leaving 1-1/2 to the garage. Once the tankless is taken off, that leaves 1-1/4 running to the generator on the right side of the house.

    Another option is to locate the meter at the left side of the house next to the backup generator. That makes the generator very easy. Since there's "only" 480k running into the house, I only need 1-1/2 to reach the mechanical room and drop off from there.

    The second option is more piping, but smaller piping. It also requires that the main line into the house go through either the crawl space or the attic. The attic is easier to work in, but a harsher (temperature) environment. Crawl is somewhat cramped, but more temperature stable. Also requires drilling the foundation in two places and the main pipe entering just a few inches above grade. Of course one hopes never to have a leak in a gas piping system, but if one did ever develop over the years, it seems the crawl would show it quicker since most of the breathing air from the house comes from the crawl. I'm probably over thinking this...

    Thoughts?
     

    Attached Files:

  2. wwhitney

    wwhitney Well-Known Member

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    Location:
    Berkeley, CA
    What pipe material are you planning for the interior runs?

    How about the meter at location A, with an immediate manifold to supply 3 separate runs? One underground outdoor run to the generator, one run to the tankless (and possibly that heater behind the garage), and one run to everything else.

    Cheers, Wayne
     
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  4. makemenuconfig

    makemenuconfig New Member

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    Thanks Wayne.
    I've only ever piped in black iron, so that is what I was planning. I had not considered an outdoor underground run for the generator, it's not a bad idea.
     
  5. Jeff H Young

    Jeff H Young In the Trades

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    Ive only worked with one gas company and They had to aproove the location and were a little pickey they had final say they didnt want them hard to acess or read on garage side almost exclusively
     
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  6. Jeff H Young

    Jeff H Young In the Trades

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    I ve rarely repiped gas on an entire home usually much can be used so its often piped a little differant than if everything was new. but if you want to save nothing and start from scratch thats ok . picture a little small for me cant read the small print at least not very easy . does it show current location of meter or the current piping ?
     
  7. makemenuconfig

    makemenuconfig New Member

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    Hey Jeff. The existing gas meter is right in the way of where the addition foundation will be, so it must move elsewhere. Due to that, the entire thing will need to be re-piped. I may reuse some of the pipe, but adding loads and length will require a larger pipe entering the building no matter what I do.

    The gas co. has a very specific set of requirements, both locations I showed on the drawing (which are the new possible locations) are within their requirements. They are coming out next week to consult on this, but I need to know which is my better option.

    [​IMG]
     
    Last edited by a moderator: Mar 22, 2021
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  8. Jeff H Young

    Jeff H Young In the Trades

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    since crawl space on homes isn't so common here on homes less than 60 or so years old except hillside communities on single story its through the attic on 2 story its in the 2nd floor at least 80 percent of time.
    So the attic makes sense to me . I've done tons of screwed pipe up to 2 inch basically and 2 and 1-1/2 kind of a pain . if you got good equipment and a helper no biggie though, option b might allow 1-1/4 its pretty short from meter , but whatever you sized out is what it is. don't know if this is a total gut job so you got no drywall in house ? It doesn't look a lot easier one way or another from here just gotta take a guess. separate underground to the generator is one way . how long will that take versus a tee in attic a stick of pipe and 3 90s material cost more for underground plus someone gotta dig it. and underground more prone to leak than attic. that one branch you could do from craw space as well eliminate nearly all the 2 inch . I cant walk the job but there is a few thoughts. Wayne's Idea is good too !
     
  9. makemenuconfig

    makemenuconfig New Member

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    Gas co. rep. came out on Tuesday. He thought option B was best for them, easy access and close to the main, so that's what I'm going to do.

    Anybody up for sanity checking my sizing? Attaching a drawing. Not to scale or physically accurate, but shows each fitting and length required. Blue is segment length, green is "pipe length + fitting eq. length = total length" for each appliance, and orange is the pipe size. Drawing: https://app.box.com/s/iubek0xc095smdmsa4q0p1wekdq40ek6

    Looks like I'm going to have to use 2" anyway unless I drop some stuff. For equivalent length of fittings, are you supposed to count a tee only when figuring the 90 degree takeoff, or for any path through a tee? I don't actually know, I was assuming the former. The codebook is not clear on this.

    I measured inlet pressure of the existing service at 7.4" WC. Of all the planned appliances, the most critical will be the outdoor BBQ, as it is the farthest and requires minimum 7" WC which is quite a bit higher than the others (next highest is fireplace at 5.5" WC minimum. If the gas co can set the new regulator at 7.5" WC, then I should be able to use the table for 0.5" WC allowed drop.

    I'm under 2015 IFGC, using table 402.4(2) and appendix table A.2.2 for equivalent length of fittings. This adds up to a lot since I've got a windy path working around existing ductwork and such. I'd prefer to work in the attic, so that's what I'm planning. The pipe will see some temperature swings, is any consideration needed for pipe expansion?

    Thanks for the help!
     
  10. wwhitney

    wwhitney Well-Known Member

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    Location:
    Berkeley, CA
    So, the longest length method is overly conservative. You may be able to use 1-1/2" pipe with a little reconfiguring and using a more exact method.

    On the reconfiguring, your piping layout is very much a single trunk with very short branches off it. If looked at as a binary tree, it would be very lopsided. It would be more efficient to have a balanced binary tree. Meaning, e.g. that if your main line from the meter is carrying 600 CFH, at the first point it splits, each side carries 300 CFH. Or you have a little manifold (multiple tees) and split it into three runs of ~ 200 CFH. Which you could do with one run to the Tankless, one run to the top right group of 3 appliances, and one run to the other 3 appliances.

    The longest length method has the advantage that it's direct: for each segment, you look at the longest length from meter to appliance fed by that segment, which tells you the row in the "allowable CFH" chart to use, then you look across that row until the entry exceeds the CFH that segment carries, and then you look at the column heading to get the pipe size. The method tells you that a 1-1/2" pipe can carry 600 CFH for 100', so if you are able to reengineer the branching of your piping structure to get every appliance within 100' of developed length from the meter, you could already downsize the main trunk to 1-1/2". Probably hard to get there, as your longest length is currently 164', but it might be possible.

    For a more exact method, you don't get a direct answer; rather you have a trial sizing, and you get a pass/fail for it. [And since you already know a 2" trunk works, you'd try a 1-1/2" trunk.] If it fails, you figure out where to upsize and try again. The easiest method would use an "allowable length" chart instead of an "allowable CFH" chart; each row would be labeled by the CFH carried, and the table entry would the longest allowable length at that CFH and that pipe size. That's the length at which the pressure drop matches the allowable pressure drop for which the table was constructed. Since pressure drop is proportional to length, you can divide your actual length by the allowable length and get a fraction (or percentage) of pressure drop budget used by that segment. Then you do that for each segment (just using the segment's length between branching points) and label the segment with the fraction (or percentage). Finally you check by seeing if for each appliance, adding up the fractions (percentages) from the meter to the appliance gives you a number above or below 1 (100%).

    Fairly easy if you have an allowable length chart. One can be made from Equation 4.1, but that's a bit of trouble. I'm not sure where to find one now. 15 years ago I used one that came in the Wardflex (a brand of CSST) Technical Guide. Or with interpolation you can use an "allowable CFH" chart: start at the column for the pipe size of your segment, read down until you find the CFH just below and just above your segment CFH, read across to the length heading on the rows, and interpolate between them. Not quite as accurate, as the CFH is not linear.

    Hope this helps.

    Cheers, Wayne
     
  11. mikha'el

    mikha'el Member

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    Off topic - when I had my last house built the plumber's apprentice asked where I wanted the gas meter. I said how about the back corner... so that's where he ran his pipe. Couple months later the same apprentice was out there re-routing the line to the front corner... I made a deal with his boss to dig the ditch for him, though. :rolleyes:
     
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  12. Jeff H Young

    Jeff H Young In the Trades

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    I've been using an old UPC gas sizing system forever Not even sure if its still sized the same but looking over your drawing everything looks very close to what Id expect you've long run with heavy demand near the end so its kinda big as expected
     
  13. makemenuconfig

    makemenuconfig New Member

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    Seattle Area
    Thanks all for the advice! Moving forward with the 2" through the attic. About half way done with the project (furnace moved + piped in, 2" main up to the attic, brought the B-vent up to code, and scattered the 50' of 2" pipe). Now I just have to get the 50' installed, down the side of the house, test, and get it inspected.

    Put what I have so far on a 10lb test. After about 4 hours it went up to 10.5lb, but after 8hr was back down to 10lb. Since the temperature was still higher, I expected the pressure to stay above 10. Bubble tested every joint twice and couldn't find anything. Finally found some bubbles on a joint that I installed two years ago. I'm sure it wasn't leaking back when I installed it, because I left it on a 10lb test for days prior to inspection. I don't know if it leaks at low pressure. It's okay because it gets ripped out in a month anyway once the meter has been moved.

    Now I'm questioning my abilities. What would cause a leak after just a few years? This joint was near where the new work starts, so perhaps it saw some vibration recently. This was 1-1/4" pipe, USA fittings and a factory nipple (probably imported, can't remember). I use rectorseal Tru-Blu (with PTFE in it) applied until it fills the threads. I don't use any tape. I tighten until it would be really hard to go another turn with an 18" wrench. The pipe is supported pretty well . Thoughts?
     
  14. Jeff H Young

    Jeff H Young In the Trades

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    there really isnt much to say about why it leaks now and why did leak befor and went unnoticed or never leaked till yesterday other than maybe this or maybe that. an 18inch wrench I belive marginal on 2 inch. been a while since commenting on this subject but most pipe machine field cut threads arent great or at least many arent great, fittings vary many many factors. some fitters like tape some like dozens of differant types of dope, some use both (I do) supposed to use certain ptfe tape and its the code but personaly I dont think white tape is bad but not arguing that its not legal for gas .
    Where your leak is either unscrew inspect and re dope or try tightening it till bubbles stop and then check other end if that end leaks then you have no choice to unscrew.
    Id recomend a cheater on that 18 incher or a 24 and a little more muscle . factory nipples and usa fittings shouldnt leak that easy but leaks and luck are factors
    meanwhile youll be guessing at how much leak is coming from the bad joint and whether that is the only leak. you sound to be doing well trublue is very good stuff in my opinion , Ive never bought it but used it working for another contractor and kept a partial can used it here and there really liked it but I could use 5 differant kinds and like them all for differant situations. Keytite and Tape is my favorite way of gas piping a system. or just a few joints at an appliance hook up just dope is fine with me.
    good luck minor setback , and smart of you to test as you go.
     
  15. Tuttles Revenge

    Tuttles Revenge In the Trades

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    I"m with Jeff on the pipe wrench.. Go with a bigger wrench on that 2". Its better to have too much leverage and only go 75% than too little leverage and go 110% capacity.
     
  16. makemenuconfig

    makemenuconfig New Member

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    Clarification: I am using a 24" wrench on the 2" pipe. The leaking joint in question was an old one which was 1-1/4" which I would have used an 18" wrench on. It won't budge at all. Not really kosher, but I threw a little dope on to see if I could get it to hold for the test. Since it gets ripped out in a month, I'm okay with that. I'll re-test the entire system again once the meter switchover happens to be sure.

    However the planned route for the new line in the attic is tight quarters. I won't be able to get a 24" wrench on the pipe and clear the roof sheathing. I've tightened all the fittings on one end before I loaded the pipe into the attic, but the other end of each pipe I'll have to make up in the attic. Might just have to give it all I've got with the 18" or see if I can get a cheater on it. Was almost thinking about using a rubber mallet impact driver style to get an extra 1/4 turn out of it...
     
  17. wwhitney

    wwhitney Well-Known Member

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    I don't quite follow. You only need about 45 degrees of rotational clearance for your pipe wrench, making up the joint 1/8 turn at a time Although that would get old quickly if you have a lot of joints to do.

    Cheers, Wayne

    P.S. For smaller sizes (1" and below) I use the protocol hand tight plus 1-1/4 to 2-1/4 more turns, shooting for 1-1/2 to 2 turns when I don't have to line anything up. What's the protocol for 2" pipe?
     
  18. fitter30

    fitter30 Well-Known Member

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    With the right pipe dope fittings don't have to be super tight to be leak free. Expando is a powder mix with water or blue monster tape and anaerobic dope. My definition of tight is different than yours all depends on age and size. Offset pipe wrench works great in tight places but their expensive.
     
  19. makemenuconfig

    makemenuconfig New Member

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    There is a 2x6 brace running the length of the building in the attic. I've lined it up so the pipe can rest on strut along this brace. It's a convenient spot for the pipe to live. However the brace gets in the way of the pipe wrench teeth, so the 24" wrench literally won't fit. Here's a photo with the 18" wrench for reference.

    IMG_0577.jpg
     
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  20. wwhitney

    wwhitney Well-Known Member

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    Obviously it's awkward in the confined space to get the proper leverage on the pipe wrench. But in your picture, a longer wrench could still swing from a little before 3 o clock to a little after 12 o clock unobstructed, almost a quarter turn. So after your 18" wrench ceases to be effective, you could switch to the 24" wrench for a few more tries.

    Cheers, Wayne
     
  21. makemenuconfig

    makemenuconfig New Member

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    Working on it tomorrow. We'll see how it goes. Thanks guys.
     
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