SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I guess you've got two options...

1. Raise the backflow.
2. Replace the backflow with something that can be below the level of the zones (RPZ or DC if DCs are allowed in your area).

Well, yea, you can do that.

I even though of adding that as a third option, but then you're not really "fixing" the existing system, you're actually creating a 2nd system because you'd have to tie into the main before the existing backflow, run that new main to the new zone, and install the 2nd backflow above the height of the new zone. Now generally speaking (now knowing the particulars of your layout) that just seems silly and MIGHT be more expensive than neccesary. For example, which is cheaper (and either one could bepending upon the length of the run and the cost of the backflow) MOVE the existing backflow to the new location (requires enough pipe to go from existing main out to the new location and back to the existing valves) or purchase a 2nd backflow to create two systems (and are you required to get a plumber to mess with backflow preventers in your area?).

Replace the PVB with an RPZ and you got all bases covered, no matter where you happen to be located. You lose at least another 5 psi with the RPZ.