Nesting Couplings

Discussion in 'Irrigation' started by Dirty Water, Aug 27, 2005.

  1. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    I like to use nesting couplings as reducer bushings, because I can stock one part and use it for two purposes.

    However, I've found that when I'm pulling a lateral line that consists of say, 40' of 1" and 20' of 3/4", 1 out of 10 times it will pull apart where it bushes down during the pull.

    I usually bevel a 3/4" nesting coupling, and glue it directly into the bell of a 1" pipe, and then glue in the 3/4" pipe. This failure is too high in my opinion, and it always happens in that spot.

    Does anyone think that switching to a regular style bushing would work better? Or perhaps a different glue (I use IPS 725 without primer)?
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,997

    Seems to be more trouble than it's worth, to reduce pipe size like that. This would be an opportunity for you to experiment with glues and primers. I think your application is pretty much outside the box, but maybe worth exploring.
     
  3. sheshovel

    sheshovel LawnSite Fanatic
    Posts: 5,112

    Yea why would you install 40' of 1" and 20' of 3/4"??
    I always use adaptors and nipples or n=make my own slip nipple then adapt if I have to go from one pipe size to the other
     
  4. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    See, I like to properly size my pipe, I know few people do it anymore, but I usually run 1" or 1.25" to the first few heads, then go down, ending with 3/4" to the last head.

    This allows me to use a 3/4" female adapter as my last fitting as well.

    Jesse Stryker has the mathmatical formulas of friction loss and pressure gain from pipe sizing on his website. Using those, he states that in most cases, the only real gain you get from sizing your pipe is that its cheaper. If I need to run 1.25" to the first 2 heads of a 8 head zone (15 gpm or so at 50 psi), theres no reasion to run it all the way.

    I occasionally cut a 2" sch 80 nipple in half, and use it slipped into a tee instead of a male adapter when installing 2" valves, but thats about the only time I do that.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,997

    I suspect the original intent behind the downsizing of the last segment of pipe was to reduce the effect of the water hammer when air finished rushing out of the last sprinkler in the line. A smaller pipe size would have some braking effect. I think this goes back to the days of waeker poly pipe and poly cutoff risers. I think today's product is stronger, and the 'sizing' less critical. Besides, for a standard 3 gpm rotor, you could run the last two heads of a lateral on 3/4 and see no significant loss of performance. If it were mist heads, even more heads might use the 3/4 lateral.
     
  6. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    First, I would suggest primer (saw that one comming didn't you?).
    Second, are you getting the reducer to bottom out in the bell? Try shortening the bell so the bell is only as long as the glue joint you are making. This may not sound like a big deal, but a bell is strongest at the shoulders, and if your only gluing into the last half, that may be part of your problem. Does the nested fitting have a shoulder that prevents it from being shoved on down into the bell? (no frame of refrence, you and boots have both mentioned these, but I havent seen them for sale in my area) Primer and make sure your glueing into the bottom of the bell. Hope that helps.
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,997

    A lot of companies make nested couplings, not just Dura, but they may not be NSF-approved, due to their thinner walls. Or maybe the local supplier doesn't feel like having a second bin of couplings taking up space.
     
  8. MikeK

    MikeK LawnSite Member
    Posts: 145

    I understand why you are using 3/4 inch pipe and the way you are using it is prefectly acceptable. Step back and think for a moment how many parts you would have to stock if you just did every standard residential system with 1" pipe. You would eliminate a bunch of extra fittings.
    How much time does it take to screw around with changing pipe sizes? It appears that in your area, everything is done with PVC. You appear to be an innovative thinker, what are your thoughts about changing to 1" poly pipe?
    In MN, all residential systems are 1" poly. we use PVC if the system requires 1.5" pipe or larger.
    In a standard, 6 zone resi system, we can pull all of the pipe, 10 to 12" down in 1 hour to 1 hour and 15 minutes, on average. My personal best is 45 Minutes flat. The cost of the pipe in a sprinkler system is minimal compared to labor costs. even though switching to 3/4 inch pipe on the last few heads makes sense from a material savings standpoint and does not effect the system performance, I am willing to bet that you could install systems in fewer man hours if you just stuck to 1" pipe. Give it a try and let us know how it turns out.
     
  9. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Mike, you are right on the money about Poly. Nobody does it out here...yet.

    We just got a poly laying blade (instead of pulling) for our 410, and we will expirement with poly systems and blazing saddles as soon as the summer/fall rush dies down.
     
  10. DGI

    DGI LawnSite Member
    from SE Mich
    Posts: 173

    The way that I pipe out a domestic water tap residential with a (3/4 or 1" water line) is 1 or 1.25" mainline, depending on the size of the yard etc., and then 1" NSF poly to all of the zones. It's pretty rare for me to install 1.25" feeders on these jobs. In new subdivisions especially we'll only use at most 80% of the current water supply to size our zones. I've seen hundreds of jobs that worked great at one point with tons of pressure, but eventually 5-6 rotors at 35 ft on all 1" pipe required lots more than renozzling. With saddles and swing pipe, the routing/fitting advantage of 3/4" over 1" is basically negated in my view. The cost differential never justified the use of 3/4" (in addition to 1" as opposed to all 1") in the yard while pulling, but when fitting inserts, certain small areas made sense. We still keep a bit in the install rigs for an area in landscape bed or wherever else more pliability is desirable.
     

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