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  #1  
Old 09-25-2013, 08:29 PM
jbell36 jbell36 is online now
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3/4" Backflow or 1" Backflow? GPM

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?
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Old 09-25-2013, 09:36 PM
txirrigation txirrigation is offline
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Quote:
Originally Posted by jbell36 View Post
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?
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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Old 09-25-2013, 09:58 PM
jbell36 jbell36 is online now
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cool...pretty much what my supplier said...he says people are just stuck with the 1" way because it's a 1" system
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Old 09-25-2013, 10:19 PM
Mikegyver Mikegyver is offline
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I installed a 3/4 this week on a 12 GPM system. I'm thinking the cutoff is 15 GPM but not sure.
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Old 09-25-2013, 11:06 PM
txirrigation txirrigation is offline
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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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Old 09-26-2013, 07:25 AM
Mikegyver Mikegyver is offline
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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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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
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  #7  
Old 09-26-2013, 02:33 PM
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jbailey52 jbailey52 is offline
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Quote:
Originally Posted by txirrigation View Post
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!

So are you supply side and feed side of the back flow still 1"?
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Last edited by jbailey52; 09-26-2013 at 02:38 PM.
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Old 09-26-2013, 06:24 PM
jbell36 jbell36 is online now
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Quote:
Originally Posted by txirrigation View Post
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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let me back up a little...when you install 3/4" backflows, are you using 1" PVC for your systems or 3/4"?
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Old 09-26-2013, 06:28 PM
jbell36 jbell36 is online now
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Quote:
Originally Posted by txirrigation View Post
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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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
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  #10  
Old 09-26-2013, 07:49 PM
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cjohn2000 cjohn2000 is offline
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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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