Why is one backflow preventer above grade, and the other is below grade in a box?
The reduced pressure backflow preventer discharges water when it fails. Plumbing code requires that the discharge point is a minimum of 12 inches above the ground. The double check valve does not discharge, and is therefore permitted to be installed below grade in a box.

Show All Answers

1. Why do I suddenly need a backflow preventer after years of not having one?
2. I just leased this building, I am now required to install backflow prevention, why wasn't this required by the previous tenant and who should pay for this?
3. Will the installation of the backflow preventer affect the pressure and or flow of my water service?
4. Why is one backflow preventer above grade, and the other is below grade in a box?