A backflow device is known as a RPZ valve. RPZ stands for Reduced Pressure Zone. This device is installed onto your plumbing system to protect your drinking water and city water supply from contaminants. RPZ valves are necessary when a house or a building is equipped with an irrigation system, fire suppression system or a large boiler. Contaminants can enter an irrigation system from fertilizer of by spraying pesticides on a lawn. Bacteria or increased mineral content can build up inside boiler or fire suppression systems as water will sit stagnant or trapped inside.

In case of a drop in water pressure, the RPZ valve will open up, dumping water out rather than allowing the contaminated water to back-flow into the water supply. Only a licensed plumber can test and certify the proper operation of an RPZ valve, and once the RPZ valve is tested, certified paperwork is forwarded by Metcalf Plumbing to the correct county or city.