How many times have you put a garden hose in a bucket of soapy water to wash the car? Or sprayed insecticide with a garden hose sprayer? Or attached a hand spray attachment to the kitchen faucet to wash your hair or the dog? These seemingly harmless actions create cross-connections that could endanger the health and safety of you, your family, and your neighbors.
The danger comes when the hose comes in contact with a harmful substance. If the pressure in the water main drops while the hose is submerged in contaminated water, then the water (and whatever is in it) could be sucked back into your pipes and the drinking water supply. Water pressure drops are not uncommon. They can occur when hydrants are opened to fight fires or during repairs to a broken water main. Fortunately, keeping your water safe from these contaminants is easy.
Backflow can also occur in the absence of a water main pressure drop. For example, some customers have backup water systems connected to their homes’ plumbing. If these systems, supplied by private wells or springs, experience a pressure increase greater than that in the public water supply system, backflow will occur. Because these private supplies are not tested and regulated by governmental agencies, they may pose a hazard to the potable water system and must be equipped with proper backflow prevention devices.
Back siphonage is backflow caused by a negative pressure (vacuum or partial vacuum) in the supply piping. Back siphonage occurs when system pressure is reduced below atmospheric pressure and potentially contaminated substances can enter into the public water supply.
Backpressure is backflow caused by pressure in the customer’s plumbing being greater than the pressure in the water supply piping, creating a situation where potentially contaminated substances can enter into the public water supply. The higher pressure in the customer’s plumbing may be from a booster pump, heating boiler, etc.
