Installation Requirements and Practices
Placement and orientation
Devices must be installed in the orientation and location the manufacturer and code require, with adequate clearance for testing and repair. RP assemblies are typically installed horizontally unless listed otherwise, with the relief valve discharge piped to a drain with an air gap. PVBs and AVBs must be installed above the critical level, and the critical level must be at least the height specified by the listing, often 6 inches above the highest downstream outlet.
Common installation rules
- No buried or concealed RP assemblies unless in a listed vault with drainage and access.
- Protection from freezing, flooding, and backflow from the drain.
- Full-port, testable shutoff valves on both sides of testable assemblies.
- Strainers upstream where required to protect check seats.
- Proper support so weight is not carried by the piping.
- Air gaps must be at least twice the effective opening of the supply pipe, with a minimum.
Traps
- Installing a PVB where continuous pressure exists downstream.
- Putting an AVB downstream of a shutoff valve.
- Burying an RP without a vault.
- Terminating a relief valve discharge directly to a drain without an air gap.
- Ignoring freeze protection, which causes failures and false test results.
Rule of thumb
If you cannot see it, reach it, drain it, and test it, the installation is wrong. Access and drainage are as important as the device itself.
Worked example
An RP is installed in a pit below grade with no drain and no clearance. Even though the device is correct for the hazard, the installation fails because the relief discharge cannot be observed and the assembly cannot be tested or serviced.