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Tuesday, March 15th 2011, 8:51am

What kind of backflow prevention valves do I need?


We bought a new house in St. Louis, MO last year. Our county
requires a permit to install a lawn irrigation system and backflow preventer. I
am planning to install a new irrigation system on my yard myself.

Our home has two water outlets slightly above the ground
level. Each outlet will be connected to three inline valves for sprinklers and
drip irrigation. I guess most sprinklers will be located below the outlet. To
my best knowledge, in this case, I just need a vacuum breaker since the highest
sprinklers are located lower than the outlet. The problem is two sprinklers and
a drip irrigation tubing may be located at the same level of the outlet. So, I
am curious if I need RP backflow preventers to pass the inspection.

I see many vacuum breakers ($10-200) and RP backflow
preventers ($250-300) of different types and prices. Which one should I buy?

Thanks, :)


Supreme Member

Posts: 482

Location: Houston, Texas


Tuesday, March 15th 2011, 10:16am

You should ask your water supplier, or pretend like you are getting a permit for your sprinkler system from the city and ask what they require. You may not have a choice. Even if your drip emitters are the same elevation as the sprinkler heads (PVB) You can raise the PVB 12 inches above the tallest drip emitter. If this is not a workable idea due to the piping and head placement then you may need an RP or DC depending on the local codes.

Good Luck.

You may want to add in to the budget the cost of a backflow certification once installed. This is to insure that it is working properly after installation. As a tester myself, I was surprised how many brand new installed units failed.
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LI0006121, BPAT0011021, CI0009500


Supreme Member

Posts: 5,292

Location: Metro NYC


Wednesday, March 16th 2011, 7:01am

Why two connection points for one sprinkler system? Only one is really needed, unless there is something unusual about the property. (and if you are referring to hose bibs, back up and start over with a real supply connection)

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