# Backflow question



## BIG1RED9 (Sep 9, 2019)

Hello all,
New to this forum and over time I am quite sure I will be asking lot of questions, I have a lot to learn.
From what I have read, in the attached drawing, sprinkler heads 2 and 3 should not be installed because they are equal to and higher than the PVB I have installed. Our water supply runs at 70 psi. Our water meter is 15 feet higher than than the PVB or supply to the house. I am puzzled because to me logically, water will flow out of sprinkler head 1 with very little if any pressure under any condition I can think of. I must be missing something but can't figure it out.

Thank you in advance for any info.
Don


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## g-man (Jun 15, 2017)

A backflow device is there for when there is no water pressure in the inlet (city side). A PVB needs to be about 12in above any downstream head. Any water from your head 1 can flow backwards from gravity. Yes it is an overkill, but it is the install instructions. For this setup you should use a RPZ valve.


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## BIG1RED9 (Sep 9, 2019)

Thanks


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