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

No backflow preventer can be buried, period.

Double Check Backflow can be buried and it's height relative to sprinkler heads doesn't matter. But your local building codes may not allow it.

The height of an RPZ relative to sprinkler heads doesn't matter either, but they pretty much have to be installed 1' off the ground (they have a relief valve of some sort. Part of the way the unit works is that if it can not maintain the pressure drop across the device that insures the water can't backflow, water squirts out of this vent to keep the water source protected. But if unit becomes submerged, this venting could fail and allow water to backflow. So you can't bury an RPZ unless it's a very special situation where the "hole" has a certain level of drainage such that it's impossible for the unit to become submerged.) RPZs are pretty much the cadillac of backflow devices, and when properly installed would be allowed just about anywhere.

Wet Boots,
Time to learn me some more

Obviously I was busy typing up my response when you already posted yours and obviously our statements are in conflict.

What is wrong with burying a DC (assuming that it's in a meter box where it can be accessed for testing).

(Let's not even get into my statements of burying an RPZ. I've read that it can be done, but only in very special situations, say the side of a hill where the meterbox has a 6" drain hole that discharges out the side of the hill... or something like that).

Buried means covered with dirt, either in direct contact with the device, or in a box or pit where the cover of said enclosure is covered with dirt. Such a practice would never pass an inspection. (that matter of access, as you pointed out)

The RPZ in an underground pit is a trickier situation, and I'd not lose sleep over upgrading an old DC valve in a dry deep meter pit to an RPZ, even if I wouldn't choose to do it that way in a brand-new installation.