In a previous post, we looked at what a cross connection was. Now we will discuss the methods and devices used for backflow prevention. Once you find a cross connection, there are two actions you can take: remove the cross connection or use some method of prevention to keep contamination from entering the water supply.
The best type of backflow protection is the one able to handle high hazards (can cause death). We have three ways to stop high hazards: reduce pressure zone (RPZ), air gap or barometric loop. An RPZ is the only device that can handle high hazards. The picture below shows how an RPZ works.
The best protection you can have against high hazards is an air gap. An air gap is a physical separation from where the water leaves the pipe to where it is to end up. Installation is very important for an air gap. An air gap must be two times the inside diameter of the pipe or one inch, whichever is greater.
The last method for handling high hazards is a barometric loop. The barometric loop consists of a continuous section of supply piping that abruptly rises to a height of approximately 35 feet and then returns back down to the originating level. It is a loop in the piping system that effectively protects against back-siphonage. It may not be used to protect against back pressure. Its operation, protection against back-siphonage (not back pressure), is based upon the principle that a water column, at sea level pressure, will not rise above 33.9 feet.
In the next post on cross connection, we will look at devices for low-to-medium hazards. CG “Tar Heel”