IPC 607.3 (thermal expansion control) / project specification
What it means on the job
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).
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- whats-wrongHigh-Rise Plumbing PRV Installation
Related IPC sections
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
A PRV is a closed-system-forming device: once it is in the line, water heated by a storage water heater downstream has nowhere to expand back to. IPC 607.3 requires thermal expansion control where a storage water heater is supplied through a pressure reducing valve, check valve or backflow preventer. Note the trigger — it is the water heater, not the PRV alone, that creates the requirement. In UPC jurisdictions the parallel rule is UPC 608.2, which calls for an expansion tank downstream of the regulator.
IPC 607.3.2
When a backflow preventer or check valve is installed on the water service (creating a closed system), a thermal expansion tank is required. Without it, heated water expanding has nowhere to go and can cause dangerous pressure buildup.
IPC 608.1
A garden hose submerged in a pool creates a direct cross-connection. If a back-siphonage event occurs, contaminated pool water can be drawn into the potable supply. Hose bibbs must have vacuum breakers and hoses must never be submerged.
IPC 608.15.1
Faucets and fill valves must maintain an air gap of at least 1 inch or two pipe diameters (whichever is greater) above the flood-level rim of the fixture. A spout that can be submerged creates a backflow risk.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.