Cross Connection Control

Customers use water for many different purposes, and the water may come in contact with other substances not fit for consumption. This connection between clean water and other substances is called a “cross-connection.”

It is a logical assumption that because water is always under pressure, it can only flow in one direction. However, can it flow the opposite way from its intended direction? The answer is yes, and when it does it can cause disastrous results. Water will always flow toward the point of lowest pressure.

If a water main in the public water system should break, or if a fire occurred and the fire department opened several hydrants, the pressure in the water mains could drop dramatically, causing a reversal of flow. The potential for this reversal of flow is why Jefferson PUD is concerned about the possibility of contaminants or pollutants being siphoned back into the water system.

When the plumbing at a residence is connected to the potable water supply, and it is connected to piping carrying another fluid or gas, such as an air conditioner containing chemicals to kill algae, the contaminant could be drawn back into our water mains. A garden hose submerged into a hot tub or swimming pool, or inserted into your car’s radiator to flush out antifreeze, or attached to a fertilizer sprayer, could siphon these contaminants back into our water mains. Incidents such as these have been documented throughout the country and have happened all too often.

Fortunately, back flow from a cross connection can be prevented. Jefferson PUD’s Cross-Connection Program protects the water system from contaminants by ensuring that customers have properly installed and maintained back flow prevention devices.

What is a Cross-Connection?

A cross-connection is defined by the Washington Administrative Code 246-290-490 as “any actual or potential physical connection between a public water system or consumer’s water system and any source of nonpotable liquid, solid, or gas that could contaminate the potable water supply by backflow.”

What is Backflow?

Backflow is the undesirable reversal of flow of water or other substances through a cross-connection into the public water system or consumer’s potable water system. There are two types of backflow—backpressure and back-siphonage.

What is Backpressure?

Backpressure means a pressure (caused by a pump, elevated tank or piping, boiler, or other means) on the consumer’s side of the service connection that greater than the pressure provided by the public water system and which may cause backflow.

What is Back-Siphonage?

Back-siphonage is backflow caused by a negative pressure (i.e. a vacuum or partial vacuum) in the Public Water System or consumer’s system. The effect is similar to drinking through a straw. Back-siphonage can occur when there is a stoppage or water supply due to nearby by firefighting, higher than normal rate of water withdrawal, a break in a water main, etc.

What are Backflow Preventers?

Backflow preventers are mechanical devices designed to prevent backflow through cross-connections. However, for backflow preventers to protect as designed, they must meet stringent installation requirements.