Backflow Information

Backflow Prevention

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?

One method of contamination, called “back siphonage”, occurs when a contaminate is drawn back into the public water system due to a loss of pressure in the supply line.

The following are just a few examples where contamination could occur:

A cross connection between the public waterline and a private well containing E-coli or other bacteria.
A water hose left in a bucket of car cleaning soap, or one stuck in the radiator to flush out the old antifreeze.
A hose left in a cattle watering trough or a mop bucket.
A fire sprinkler system that allows chemicals from the sprinkler tank to get back into the water main.

But there is another way contamination can occur. It is called “backpressure” and a common source is heating system boilers. Many boilers 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 waterlines. Other possible sources of contamination include pressure washers, mortuaries, permanently connected restaurant dish washers, manufacturing machine cooling lines, soda/beverage machines, garden aspirator sprayers, and air conditioner cooling towers.

Types of Backflow Preventers

‍There are several methods or devices employed to combat possible sources of contamination.

Air Gap

An air gap is the highest achievable level of protection because it is an actual physical separation between the public water supply and the point of usage. The gap must be at least twice the diameter of the supply inlet, but never less than one inch. 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 back siphonage and backpressure.

Double Check (DC or DCVA)

This assembly is similar to a reduced pressure principal assembly because it has two spring-activated check valves and two independent cutoff valves, however, it does not have a center relief valve. It is approved for low hazard protection from both back siphonage and backpressure.

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 back siphonage. It is approved for high hazard back siphonage 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 low hazard back siphonage.

Augusta Water Cross Connection Control Policy

The purpose of the Augusta Water Cross Connection Control Policy is to eliminate and/or control cross connections in order to protect the public potable water supply. These Rules and Regulations are based on the authority and requirements of the federal Safe Drinking Water Act, Virginia Code, Virginia Department of Health Waterworks Regulations, Virginia Plumbing Code, and Augusta County Code, Chapter 24 Water and Sewer Service.

Helpful Resources

For customers subject to the Cross Connection Control Policy who employ a backflow preventer, each backflow prevention device must be tested on an annual basis. The Backflow Prevention Assembly Test Report must be provided to Augusta Water annually following the testing of the Backflow Prevention Assembly. We are also pleased to provide a list of local Backflow Testing Companies with contact information. Each customer/company is responsible for ensuring the tester is properly licensed with Virginia Department of Professional and Occupational Regulation (DPOR) at the time of the backflow device testing.