yard was uphill, I can definitively state that the backflow preventer was several feet beneath the highest sprinkler head.

I say bury them, but they're below grade inside one of those plastic valve vaults. With ground temps that don't freeze, that's enough to provide all the freeze protection they need out here.

But hey, if you mount them a foot above the highest sprinkler head then I guess you've got a back flow preventer that can never fail since gravity will do all the work regardless.


BTW, why do you need one with secondary water? The only reason they are required here is to protect drinking water since we don't have secondary water.