Preventing a disaster before it happens
The Safe Drinking Water Act regulates the nation’s public drinking water supplies.
Backflow prevention devices protect the water supply from contamination. The water supplier has a backflow program to protect this supply. The end user, residential homeowner or business is responsible to comply with the local plumbing codes. This, as we know, is not reality, but with backflow programs becoming more enforced and with constant education we can eliminate a large portion of the disasters associated with backflow incidents.
The Safe Drinking Water Act regulates the nation’s public drinking water supplies. It was initially focused on the treatment process until amendments were made to the law that added essential training, funding and public information, as well as source protection.
Our responsibility as plumbing contractors (trade professionals) is to provide code-compliant plumbing systems to “protect the health of our nation.” With homeowners, handymen and the “un” professionals out there, this task can be monumental at best.
Terms to know
Cross connection is the term used when we have a potential backflow condition. Cross connections are not always obvious to professionals and homeowners will shortcut these protections to save money or maybe they just have no idea of the dangers ahead when not correctly installing plumbing fixtures.
There are two types of cross connections: indirect cross connections and direct cross connections. An indirect cross connection would be the hose filling a pool. In this cross connection, back-siphonage would be the danger and not backpressure. A direct cross connection would be a water makeup line piped into a boiler system. This cross connection would be subject to back-siphonage as well as backpressure.
Backflow is the undesirable reversal of water flow caused by backpressure or back-siphonage.
An example of backpressure would be a house that has a booster system. This booster system is designed to increase the system pressure (downstream pressure) when the supply pressure is not adequate. It uses a pump and a bladder storage tank. The danger here is a failing check valve with a cross connection within the system.
A back-siphonage would be a high draw of water in the distribution system that would decrease the pressure on a branched line pulling water back into the system after it has passed the customer’s meter. An example of this would be a fire hydrant getting run over and a house close by has a hose filling their pool (cross connection). This example is an “aspirator” effect. Without backflow prevention, the chemicals can be siphoned back into the distribution system. Once repaired, these chemicals can be sent to another customer downstream.
As professionals we need to be cognizant of any cross connections and correct them before they cause health issues or even death. For a backflow incident to occur, three conditions must be met: there must be a cross connection, a hazard must exist and the hydraulic condition of either back-siphonage or backpressure must occur.
There are more than 50 pages of “backflow incidents” listed in the back of the 10th edition of the USC Manual of Cross Connection Control that were reported to the Foundation for Cross Connection Control and Hydraulic Research at USC with the first incident dating back to 1908. I would recommend reviewing this list as it contains the cause and effect in most of the incidents listed.
Over the years I have had plenty of customers remove or ask me to remove the simple vacuum breaker on a hose bib because it will not work properly with the spray handle on the end of a hose. Imagine a homeowner wanting to kill weeds with a potent weed killer that attaches directly to the hose. It’s a Friday evening and you are spraying the weeds. As you are spraying the weeds, simultaneously a driver swerves to miss a squirrel crossing the road and instead hits a fire hydrant. Your weed killer is being pulled back into the hose from the back-siphonage caused by the broken hydrant. Shortly after this occurs, the water district shuts down the water to the hydrant, makes the repair and then puts the system back online. This poison is now in the system and a disaster could result from it.
There are a few backflow devices being used for protection with applications varying on the degree of hazard. The most common devices are the double check valves seen on fireline systems, the pressure vacuum breakers commonly used on irrigation systems and the reduced-pressure valves commonly used on potable water. The reduced-pressure valves are used for the highest degree of hazard and are becoming the go-to valve for all applications, even the fireline systems.