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Circulation Relief Valve – Section 3.3.75.4.1 & 4.13

When a centrifugal fire pump is operating at churn, energy is continuously imparted to the water in the impeller, causing the water to heat. For electrical drive fire pumps and radiator-cooled engine driven fire pumps, a listed circulation relief valve is needed to provide cooling water when the pump is operating at churn.


The pipe connection for this valve must be located on the discharge side of the discharge can be observed by the pump operator. This valve should be installed in the vertical position, because installation in the horizontal position might cause the valve to fail at an accelerated rate due to obstructing material collecting in the valve seat. Failure or the omission of this valve can result in overheating and subsequent damage to the fire pump.


3.3.75.4.1 Circulation Relief Valve. A valve used to cool a pump by discharging a small quantity of water. This valve is separate from and independent of the main relief valve.

4.13.1.2 Unless the requirements of 4.13.1.8 are met, each pump(s) shall have an automatic relief valve listed for the fire pump service installed and set below the shutoff pressure at minimum expected suction pressure.

4.13.1.7 The automatic relief valve shall have a nominal size of 0.75 in. (19 mm) for pumps with a rated capacity not exceeding 2500 gpm (9462 L/min) and have a nominal size of 1 in. (25 mm) for pumps with a rated capacity of 3000 gpm to 5000 gpm (11,355 L/min to 18,925 L/min).