IPC 604.8 / Manufacturer installation requirements

IPC 504.6.2

The T&P relief valve discharge pipe must not be smaller than the valve outlet, which is 3/4". Reducing the pipe restricts the relief flow and creates a dangerous pressure condition.

IPC 604.3 / IPC Table E103.3(2)

Add it up per IPC Appendix E: three full baths (~3.6 WSFU each), kitchen sink + dishwasher (~2.5), laundry (~1.4), and two hose bibbs (2.5 each) put the building in the 18-22 WSFU range. From Table E103.3(2) at 46-60 PSI, a 3/4-inch meter-and-main is good for roughly 10-14 WSFU at typical development lengths — this load wants a 1-inch service. The 15 feet of elevation also costs 6.5 PSI (0.433 PSI/ft) before friction. Undersized services show up as pressure crashes when two fixtures run at once.

IPC 604.8 / ASME A112.26

A single PRV with no bypass means the entire residential zone loses water every time the valve is serviced. The IPC doesn't mandate duplex stations — this is a project-specification and high-rise best-practice requirement: two PRVs in parallel with isolation valves so one can be rebuilt while the other carries the zone. Know the difference between what code requires and what the spec you bid requires — both get you red-tagged on this job.

IPC 605.11.2

Lead solder is prohibited on any pipe or fitting in a potable water system. Only lead-free solder (0.2% maximum lead content) may be used per the Safe Drinking Water Act and plumbing codes.

IPC 605.24

Dissimilar metals (steel valve body to copper pipe) must be joined with a dielectric fitting to prevent galvanic corrosion.

IPC 607.3 (thermal expansion control) / project specification

Don't misread the code here. IPC 604.8 only governs WHEN a pressure-reducing valve is required (static pressure over 80 psi) plus its setting/bypass rules — it does NOT mandate a relief valve downstream of each PRV. The actual code requirement is thermal-expansion control on the closed system per IPC 607.3, which is normally satisfied by an expansion tank at the water heater/closed zone, not a relief valve at every PRV. A downstream relief valve at a high-rise PRV station is still good practice / spec: if the PRV fails open, piping and fixtures rated for 80 psi could see 150+ psi. Know what code mandates (expansion control, IPC 607.3) versus what the spec adds (PRV-failure relief).