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craigwagner6

Active Member

Posts: 6

Location: USA

1

Monday, August 18th 2003, 6:36am

Pressure Drop Through Backflow Device

I have 3/4 inch feed into my basement. I was going to tee off this line where it enters the basement to feed my system. I understand why I need to upsize the pipe to 1 inch (pressure drop considerations) when feeding the valves and heads. Would it be ok to continue the 3/4 inch copper a few feet to a 3/4 inch double check valve and then upsize to 1 inch PVC to the valves and then the sprinkler heads. OR...do I need a 1 inch double check valve. What is the pressure drop through a 3/4 inch double check vs. a 1 inch double check.

Rays Sprinklers

Supreme Member

Posts: 493

Location: USA

2

Monday, August 18th 2003, 2:22pm

Hey,
What i would do....is purchase a 1" double check valve either Watts or Febco from Sprinkler warehouse. Depending on wether your pressure and gpm is high....i would tap in and install a bullhead tee (3/4" x 3/4" x 1") and transfer to 1" right at the connection.....just to be sure that you have adaquet flow and pressure. If you do not wish to convert to the 1" pipe at the tap...then you can tap into the pipe with a 3/4" tee, and run the 3/4 to the backflow, still using a 1" BF device. At the end of the 3/4" tap install a 3/4" x 1" male adapter....and after the backflow device stay with 1" pipe... You should install the backflow relativly closest to the tap if you are using a double check (inside, and if you change your mind and use a PVB, that must be installed outside the home...After the backflow device i recommend using copper or PVC (one or the other) to head to the valves....remember to install a tee and cap it off with a threaded cap....so you can winterize your system....(the most common way when using a DC is to run copper outside and install a heel tee which has the threads on the leg...so the cap points up...and run the line to the valves(if you use copper after the DC) ..... anyway...definatly use a 1" Double Check [:D]
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers

craigwagner6

Active Member

Posts: 6

Location: USA

3

Monday, August 18th 2003, 3:08pm

Ray

Do you recommend a DC or a PVB? $$ wise the PVB would save a few bucks.

What would you consider a high enough psi and gpm for a DC or a PVB? Is there a difference in pressure drop between the two? I have measured my psi at 55-70 lbs. I haven't measured my gpm yet since I haven't tapped into my 3/4 inch line yet. I wouldn't get an accurate gpm through my 1/2 inch outside faucet.

I was also planning on going copper to the backflow and PVC from there to the valves then poly to the heads.

Thanks
Craig

SprinklerTalk

New Member

Posts: 3

Location: USA

4

Tuesday, August 19th 2003, 12:23pm

Craigwagner6,

I recommend the double check valve assembly since your local building code requires it.

See Local Code Lingo Topic:
http://www.sprinklertalk.com/forum/topic.asp?TOPIC_ID=386

Both the PVB and DCA typically lose about 5 psi through the device. The DCA will lose a litle more than the PVB, but not enough to make your decision based on pressure loss through both devices.

[:)]
Steve
SprinklerTalk

Rays Sprinklers

Supreme Member

Posts: 493

Location: USA

5

Tuesday, August 19th 2003, 1:43pm

Hey,
Definatly use the Double Check valve! The PVB must be installed 12-18 inches above ground and outside, while you can place the double check inside right after your tap! Changing over to PVC to the valves will be much eaiser. Definatly use the Irritrol 2400T valve for the inline valve. ......... Either choose a Febco or a Watts backflow! [:D]
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers

craigwagner6

Active Member

Posts: 6

Location: USA

6

Tuesday, August 19th 2003, 1:45pm

Thanks,

Everyone has been a BIG help!

Rays Sprinklers

Supreme Member

Posts: 493

Location: USA

7

Sunday, August 31st 2003, 1:09pm

Glad we could be a help!
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers

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