Pressure-reducing valves, IPC 2021 Section 604.8
Where water pressure within a building exceeds 80 psi (552 kPa) static, an approved pressure-reducing valve must be installed. The trigger is 80 psi, not 100 or 125 psi; waiting for those figures leaves piping above 80 psi.
The valve setup has three parts:
- It conforms to ASSE 1003 or CSA B356. A valve of any listing does not meet the section.
- It is installed with strainer. Omitting the strainer fails the wording.
- It reduces the pressure in the building water distribution piping to not greater than 80 psi static. Setting it to 90 psi fails. The limit is stated as static pressure, not dynamic pressure.
A building at 95 psi static needs this valve, set to bring distribution piping to 80 psi static or less.
Backflow, IPC 2021 Section 608.1
Section 608.1 requires a potable water supply system to be designed, installed and maintained so as to prevent contamination from nonpotable liquids, solids or gases introduced through cross connections. It covers the whole potable system, not only sprinkler connections.
Table 608.1 lists which devices are allowed for each application, such as the reduced-pressure principle assembly (RPZ), double check and vacuum breakers, along with the standard each device must meet. Two traps:
- The RPZ is not required everywhere. The table picks a device application by application.
- A cross connection protected only by a check valve is not allowed. The rule is to prevent contamination.
An RPZ is a backflow device under Section 608, not a pressure-reducing valve under Section 604.8.
T&P relief valve discharge, 2024 IRC P2804.6.1
A water heater's temperature and pressure relief valve discharge pipe must terminate:
- Not more than 6 inches above the floor or waste receptor flood-level rim.
- At least two times the discharge pipe diameter above it. For a ¾-inch pipe that is 2 × ¾ = 1½ inches.
Twelve inches doubles the maximum. Using ¾ inch uses one diameter instead of two. Giving only the 6-inch maximum misses the two-diameter air gap.