3/4" Backflow or 1" Backflow? GPM

Discussion in 'Irrigation' started by jbell36, Sep 25, 2013.

  1. jbell36

    jbell36 LawnSite Bronze Member
    from KANSAS
    Posts: 1,258

    we do mostly residential installs and i was thinking what the difference between a 3/4" and a 1" double check backflow assembly was? most all of our installs are on 5/8" meters and that is at a flow rate of about 10-12 GPM...if i remember correctly, isn't a 3/4" double check capable of about 20 or more GPM?

    my question is, would it make more sense to use a 3/4" instead of a 1" in this situation for these reasons:

    1). cheaper
    2). fits in a box easier, not as crammed as a 1"

    am I missing anything?
     
  2. txirrigation

    txirrigation LawnSite Senior Member
    from Texas
    Posts: 977

    We do it 12 times a week. The performance is better out of a 3/4 @ 12 gpm because the checks fully open and do not "float." Like you said, it fits better in the box and you can get the wye strainer in the box and service it easily.

    Do it!
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  3. jbell36

    jbell36 LawnSite Bronze Member
    from KANSAS
    Posts: 1,258

    cool...pretty much what my supplier said...he says people are just stuck with the 1" way because it's a 1" system
     
  4. Mikegyver

    Mikegyver LawnSite Bronze Member
    Posts: 1,810

    I installed a 3/4 this week on a 12 GPM system. I'm thinking the cutoff is 15 GPM but not sure.
     
  5. txirrigation

    txirrigation LawnSite Senior Member
    from Texas
    Posts: 977

    Make sure your using sch. 80 in and out, it's also a good idea to use a brass nipple between the dcva and the wye.

    This has been a public service announcement...
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  6. Mikegyver

    Mikegyver LawnSite Bronze Member
    Posts: 1,810

    I usually use Sch. 80 between them but this time we just used class pipe and fittings because we were going from 3/4 double check to 1" wye strainer
     
  7. jbailey52

    jbailey52 LawnSite Bronze Member
    Posts: 1,057

    Posted via Mobile Device
     
    Last edited: Sep 26, 2013
  8. jbell36

    jbell36 LawnSite Bronze Member
    from KANSAS
    Posts: 1,258

    let me back up a little...when you install 3/4" backflows, are you using 1" PVC for your systems or 3/4"?
     
  9. jbell36

    jbell36 LawnSite Bronze Member
    from KANSAS
    Posts: 1,258

    i always use brass closed nipple fittings now because i have had to repair a few (that i did not originally install)...this is a fitting that i will not skimp on, have even seen schedule 80 break a few times
     
  10. cjohn2000

    cjohn2000 LawnSite Senior Member
    Posts: 553

    Watch out for those "molded" sch. 80 nipples. Machined never leak. And never, ever, ever paste a SPEARS thd. union. We set our backflows on unions and what I was taught is to use slip unions and paste plastic into brass and tape plastic to plastic
     

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