Medical treatment of people and animals, pharmaceutical or chemical research and manufacturing, dairies, nurseries, stadiums, abattoirs, combined fire systems etc. Most of the municipal bylaws underpin this by stating that it is the responsibility of the Homeowner (Not the tenant) to have this maintained once a year. A record must be kept of when this maintenance was done and by whom. The unit must be overhauled or replaced every five years and a record of this must also be kept. A national regulation requires that any Backflow Preventer discharges where it is visible so that any malfunction of the system can be readily detected and attended to. This means that we cannot hide this valve somewhere in a duct or a manhole, it must be above ground level where the discharge is visible. If theft is a factor the valve may be closed with a surround, but the discharge must still be where it is visible. Below is a drawing of a typical installation. How does the valve work? There is a mechanical check valve at the inlet and outlet of the valve. In the middle, there is an area (Zone) that is open to the atmosphere.
As soon as water pressure enters the valve a diaphragm is pushed down, and the relief port is closed. Once this area is now filled with water the second check valve is opened and the downstream plumbing system can be filled with water. If for any reason the upstream pressure drops below the downstream pressure, the check valves will close, and the Reduced Pressure Zone will open to discharge any water in that area. If any of the check valves are faulty and are causing water to enter the Operating Chamber, a discharge of water will be visible from the Discharge Port to alert any passers-by of the system failure. It would be prudent to have a contact number near the valve so that anybody could contact the responsible person for this. A full range of spares is available from the manufacturer. Contact your local valve supplier for availability. CALAFRICA, +27 (0) 11 795 1519, email@example.com, www.calafrica.co.za Pipes, Pumps and Valves Africa - May/Jun 2021