The backflow of contaminated or polluted water into the drinkable water supply is prevented by a specially designed assembly. Back pressure, from numerous possible sources such as water pumps, boilers, heat exchangers or power washers (to name a few) can force undesirable contaminants to enter into piping that supplies drinking water. To reduce this risk, a backflow preventer can be installed. Because of the potential for health hazards on a broad scale, such systems, particularly in commercial or industrial settings where potentially toxic chemicals are used, need frequent testing. In some locations, annual backflow testing is mandated by logal authorities.
As a preventive measure, some health regulations require an air gap or backflow prevention mechanism between the delivery point of water and its use or storage to protect the drinking water system from contamination hazards. Most backflow assemblies have test cocks and shut-off valves that must be tested when installed. They also need to be tested again if relocated or repaired, and also on a periodic basis. The EPA holds local water suppliers responsible for maintaining a certain amount of purity in drinking water systems while many municipalities also require annual testing. In most cases, the law requires an air gap or double check device when backflow prevention is mandated.
All testing is done under no-flow water conditions so home owners, commercial and industrial operations, as well as hospital and continuous process industries must be well informed in order to plan and coordinate water shut downs. Test personnel follow local municipal, county and state testing requirements and guidelines as dictated by local authorities.
Field testing exists for pressure principle backflow preventers; pressure vacuum breakers; and, double check valve assemblies. Of primary concern is that the internal shut-off valves remain tight and leak free under various degrees of applied pressure.
