Backflow Prevention | Augusta Water

Helpful Backflow Documents

Backflow Prevention: What is it?
Backflow Prevention is simply a method of keeping contaminating substances from entering the public potable water supply. It has nothing to do with sewage “backing up” or clogged storm drains. It does affect every person who uses any public water supply and is one way to help prevent sicknesses or injury due to the use of, or the consumption of, contaminated water. Waterborne bacteria can cause digestive disturbances, diarrhea, allergic reactions and in severe cases result in death. Caustic or other chemical substances entering the public water supply could result in widespread instances of skin irritation, tissue damage, or infection, and, if ingested, might have the same effect as drinking lye or other poisons.
What causes the contamination? It could be one of many things. A possible source for it might be a cross connection between the public water line and a private well that has E-coli or other bacteria present in it. It can come from a water hose left in a bucket of car cleaning soap, or one stuck in the radiator to flush out the old antifreeze. It can be that same hose left in a cattle watering trough or a mop bucket. It can be from a fire sprinkler system that allows lead from the sprinkler distribution piping to get back into the water main. Those are examples of what is called, backsiphonage. But, there is another way that contamination can occur. It is called backpressure and a common source of that kind of contamination is heating system boilers. Many of them are connected directly to the public water supply yet use anti-scale chemicals which are often toxic. The heating of the water often raises the pressure in the boiler lines to a pressure level above the supply line pressure. That pressure could cause the chemicals in the boiler to be forced backward into the water lines. Other sources of contamination are pressure washers, mortuaries, permanently connected restaurant dish washers, manufacturing machine cooling lines, soda/beverage machines, garden aspirator sprayers, air conditioner cooling towers, and the list goes on.

To combat these possible sources of contamination, we can employ several different methods or devices. Let’s look at a few of them.

Air Gap:
An air gap is the highest level of protection that can be achieved because it is an actual separation between the public water supply and the point of usage. It must be a physical gap of no less than one inch above the tank but should actually be twice the diameter of the supply line. This method offers protection in high hazard applications since there are no physical cross connections.

Reduced Pressure Principal (RP, RPZ, or RPPA):
These devices are supplied as an assembly containing two separate spring loaded check valves, a pressure controlled relief valve (in between them), and cut-off valves on either end. They offer high hazard protection from both backsiphonage and backpressure.

Double Check (DC, or DCVA):
This assembly is similar to a reduced pressure principle assembly because it has two spring-activated check valves and two independent cutoff valves. But, it does not have a center relief valve. It is approved for low hazard protection from both backpressure and backsiphonage.

Pressure Vacuum Breaker (PVB):
This unit consists of a single spring-loaded check valve and uses an air inlet valve to allow air to enter and break the vacuum present thereby preventing backsiphonage. It is approved for high hazard backsiphonage prevention.

Atmospheric Vacuum Breaker (AVB):
An AVB is a device containing a single check valve with an opening to allow air to enter and break the back siphon vacuum. Its applications are somewhat limited and is approved only for high hazard backsiphonage.

What is a cross-connection?
Any connection between a potable water supply and a hazardous material or one of questionable quality. There shall be no such connection without the installation of an approved backflow prevention assembly in accordance to the degree of hazard of the substance involved.
What is backflow?
Backflow is the undesirable reversal of flow of non-potable water or other substances through a cross-connection and into the piping of a public water system or consumer's potable water system. There are two types of backflow--back pressure and back siphonage.
Why do backflow preventers have to be tested at least once annually?
Mechanical backflow preventers have internal seals, springs, and moving parts that are subject to fouling, wear, or fatigue. Also, mechanical backflow preventers and air gaps can be bypassed. Therefore, all backflow preventers have to be tested periodically to ensure that they are functioning properly. A visual check of air gaps is sufficient, but mechanical backflow preventers have to be tested by a certified tester, with properly calibrated gauge equipment.
What is potable water?
Water which is safe for human consumption, free from harmful or objectionable materials as described by the Health Department.
How do I know if I need a backflow prevention assembly?
A member of the cross-connection control staff may visit your property to perform a preliminary survey for backflow requirements. You may request a letter providing you with the guidelines and what action you need to take to conform to ACSA requirements.
What Kind Of Backflow Preventer Is Best?
Which of the units described is best for your needs? It depends on the individual hazard or what potential hazard exists at your site. We are happy to answer your questions regarding installation of certain devices, regulations, codes, and inspections. What are the proper applications of the devices listed and which would best fit your needs. Please see our contact us page to contact the Cross Connection Control Coordinator.

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