IPC 608.15.1

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 608.1

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 608.15.4.2

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.

IPC 704.1

For pipes 3 inches and larger, the minimum slope is 1/8 inch per foot. A slope of 1/4 inch per foot exceeds the minimum and is acceptable. While the minimum would suffice, a steeper slope within reason provides better flow velocity and self-scouring action.