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BGOFFE

Unregistered

1

Tuesday, October 6th 2015, 9:32am

Backflow Sizing & Piping

Hi All,

Just trying to read up on all I can before I go at installing my sprinkler system. My question is sizing the backflow device and piping it. I am checking with code but based on what I've read I am going to go with Reduced Pressure Zone (RPZ) Valve.

My supply is 3/4 copper in my basement. My sprinkler design is calling for 1.25" Feeds to the valves. Should I go with 3/4" backflow valve and then transition from 3/4 to 1.25" at the output of the backflow valve?

Should I transition from copper to PVC in my basement and land PVC on the input of the backflow preventer which I plan on installing outside 12" above my sprinkler heads.

Any help/advice is greatly appreciated.

SunCoLawns

Advanced Member

Posts: 111

Location: Omaha, Nebraska, USA

2

Tuesday, October 6th 2015, 10:49am

If someone designed your system with 1.25" feeds to the valves, I would think a 1" backflow would be preferable. I'd recommend transitioning to 1" copper and then taking that to the backflow, and then out into the ground and out at least 3 feet from the house. Of course you'll want a drain valve before the backflow.

Wet_Boots

Supreme Member

Posts: 5,191

Location: Metro NYC

3

Tuesday, October 6th 2015, 10:51am

You don't use PVC pipe for pressure plumbing inside a house. It lacks code acceptance for that application. You might supply more details, because going from 3/4-inch to 1-1/4 inch is uncommon, unless there are very long pipe runs involved.

BGOFFE

Unregistered

4

Tuesday, October 6th 2015, 11:30am

Yes, in my opinion there are long piping runs which is why they sized it 1.25". The longest pipe run is 140' to the valve manifold, and then another 125' to the furthest sprinkler.

SunCoLawns, You said a a drain valve before the back flow valve. Wouldn't I want it after?

I am hesitant to bury copper as I haven't had much luck with it underground. Always seems to develop pin hole leaks. This is why I was hoping it would be acceptable to transition to PVC in the basement.

Wet_Boots

Supreme Member

Posts: 5,191

Location: Metro NYC

5

Tuesday, October 6th 2015, 6:37pm

From a basement water meter, you do best to exit the foundation above ground, with copper (type L minimum), with, in order, a shutoff valve (gate valve is okay) a tee with a drain valve, your RPZ backflow preventer, and then you can transition to PVC.

SunCoLawns

Advanced Member

Posts: 111

Location: Omaha, Nebraska, USA

6

Wednesday, October 7th 2015, 8:13am

Yes, in my opinion there are long piping runs which is why they sized it 1.25". The longest pipe run is 140' to the valve manifold, and then another 125' to the furthest sprinkler.

SunCoLawns, You said a a drain valve before the back flow valve. Wouldn't I want it after?

I am hesitant to bury copper as I haven't had much luck with it underground. Always seems to develop pin hole leaks. This is why I was hoping it would be acceptable to transition to PVC in the basement.


I have been installing systems for 23 years and can't recall having an issue with an underground copper leak. Could be a climate/soil thing. Anyway, it's code around here that you have to have copper going into the ground. I have always figured it was to prevent damage caused by lawn mowers. The other issue is settling around the foundation. It is commonplace to have to fix the connection between copper and PVC if the ground around the foundation settles too much. That's why I recommend bringing the copper out a few feet.

You need to have a drain before the backflow to drain the line going to the backflow. You can install one after the backflow to facilitate winterization.

This post has been edited 1 times, last edit by "SunCoLawns" (Oct 7th 2015, 8:19am)


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