IPC 608.1

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 (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).

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 608.15.1

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.

IPC 608.15.4.2

This is a cross-connection violation. A hose connection that can be submerged below the flood-level rim creates a backflow hazard. The dirty mop water in the sink could be siphoned back into the potable water supply during a back-siphonage event. A listed atmospheric vacuum breaker (ASSE 1001) or hose connection vacuum breaker (ASSE 1011) must be installed on the hose bibb.

IPC 608.16.4 / ASSE 5013

The relief port discharge must terminate with an air gap above any drain receptor. Without an air gap, a cross-connection is created at the very device meant to prevent cross-connections. The discharge must also be visible to indicate when the relief valve is operating.