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sauropod

New Member

1

Tuesday, September 8th 2015, 11:18pm

Do I need a back flow preventer?

Hi All,

I have a slope in my yard that runs 65' up at a roughly 30 degree angle. I have 3 zones of drip irrigation on the slope with valves located at the top of the slope. My irrigation main runs to the top of the slope into the valves. The 3 valves are Rain Bird ASVFs.

I also have a single valve that supplies drip irrigation at flat ground level. This is also connected to the irrigation main.

Question- do I need a back flow preventer? I've done some research and it seems unless I get a DC (double-check) device I would need to place my back flow preventer at the top of the hill (or at least a foot above the highest irrigation line). The DC type seems it can be placed on level ground.

Do I even need a back flow preventer? What if I put some check valves up the irrigation line to the top?

Is there a risk of my irrigation back flow contaminating my main drinking water supply? I checked my local city codes and they say a back flow preventer is not required for residential use unless I am connecting a special networked water device to the main.

I live in the bay area (San Ramon, CA).

Thanks!

SunCoLawns

Advanced Member

Posts: 111

Location: Omaha, Nebraska, USA

2

Wednesday, September 9th 2015, 7:10am

That kind of application really calls for an RPZ, but codes vary by state and locality and your area sounds pretty lax. Your main water supply IS at risk of cross contamination so I would say a DCV at the least, but it would need o be tested periodically to be worthwhile.

sauropod

New Member

3

Wednesday, September 9th 2015, 12:20pm

Backflow preventer on slope

OK thanks. Sounds like I should do this right.

Assuming I use an RPZ type, I'm guessing I'm going to have to put it up at the top of the hill/slope just before my valves. Then put another type (maybe DCA?) at ground level for my last valve.

Do I need to install the RPZ horizontally or does it matter? I couldn't tell from 2 different manufacturer's installation instructions whether their RPZ preventers needed to be installed level horizontally or not, which would require me to create an odd twisting PVC setup along the slope.

thanks

SunCoLawns

Advanced Member

Posts: 111

Location: Omaha, Nebraska, USA

4

Wednesday, September 9th 2015, 4:12pm

Most RPZs must be installed horizontally. RPZs that can be installed vertically are usually N-shaped. They can be installed below downstream piping, but they must be installed at least a foot off the ground. If you are going to run your supply line all the way to the top of the hill, and your locality allows you to do that unprotected, you could get by with a PVB, but that also must be mounted at least a foot off the ground.

sauropod

New Member

5

Wednesday, September 9th 2015, 11:11pm

Backflow preventer on slope

Thanks for your prompt responses. Appreciate the help! :thumbsup:

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