Originally Posted by Mike Leary
I see no reason why a RP cannot be installed in a proper below-grade v.b., as long as a sump is installed to drain the relief
You're kidding, right? Sumps don't fail? Power doesn't go out?
If the level of hazard is high enough that an RP is spec'ed, it need to be installed where the relief can drain fully from gravity alone with no reliance on any other mechanical device. I know they get installed in basements a lot, I guess the justification is that a basement is big and can handle the flood but a VB can't even make that claim. Put it above grade and either put a hot box on it or wrap it with heat tape.
And for the record, I'm in the DCVA's should not be approved devices for irrigation systems camp. I don't think any irrigation BPV should be below grade.