Overview
When drinking water piping connects to various plumbing fixtures or water utilizing equipment a cross-connection is created. If improperly protected, contamination can result when a backflow event occurs; allowing contaminates to reverse flow from the fixture/equipment back into the drinking water piping.
What Can Cause a Backflow
Conditions that are likely to create a backflow event are typically common, but unfavorable, hydraulic events that occur within the public or private segments of the water distribution system such as: an owner or worker draining down a house or building to make a plumbing repair; a broken water main or distribution pipe; severe/widespread power outages; fire fighters using large quantities of water to extinguish a fire, or; a water utilizing piece of equipment or process creating pressures greater than those present in water distribution system.
When these unfavorable hydraulic events are occurring, contaminates can be back-siphoned into the drinking water due to negative pressures; or contaminates can back-pressured into the drinking water due to excessive pressure imposed by the water utilizing piece of equipment or process.
Built-in Protection
Modern plumbing fixtures generally have built-in backflow protection. For instance, a faucet spout terminates above the flood rim level of the sink or tub. So if the sink or tub is full of dirty water or worse, backed-up sewage, there is no possible way for backflow because of the air gap created by the elevated spout. Toilet fill valves, clothes washers, dishwashers, and refrigerator/ice makers also employ some type of built-in air gap as their method of protection.
So around the home and office, for the most part, standard plumbing fixtures do not present a hazardous condition. However, additional protections are needed for household items such as: hand held shower heads; hose bibbs; lawn irrigation; and boilers.
Why is a Backflow Preventer Required on Lawn Sprinkler Systems?
Lawn irrigation systems can backflow contaminated water into your drinking water. In order to prevent this, building codes require that these systems be protected with a backflow preventer.
