Potential Contamination Due to Backflow

What is Backflow?

Water in any system is intending to flow in only one direction; from the distribution system to the consumer. Any pressure differential between the potable water and the non-potable source can lead to backflow. When this happens, pollutants and contaminants enter the potable water supply through cross-connections where non-potable water can be connecting to potable sources. Contaminated water could be harmful to water users and lead to serious health issues. There are two types of Backflows:

Back Pressure: Whenever the downstream pressure is greater than the upstream or supply pressure in a public water system, contaminated water forcefully enters into the public water system. In a famous incident, propane entered the potable water supply as a result of backpressure from tank cleaning activities. As a result, several abodes caught fire and hundreds had to be evacuating.

Back Siphonage: Back-siphonage happens due to a negative pressure in a public water system or customer’s potable water system. The sudden vacuum causes contaminants to be sucking into the potable water supply line.

Backflow prevention prevent harmful contaminants, such as pathogens, bacteria, detrimental chemicals, heavy metals, gases and other potentially. Threatening pollutants/substances from entering the community’s potable water system. The most common types of backflow devices include Atmospheric Vacuum Breaker Assembly, reduced pressure zone devices, Pressure Vacuum. Breaker Assembly, and Double Check Valve Assembly. Must buy such products from any best bathroom hardware manufactures in your town.

Famous Backflow incidents

Backflow at a Car Wash Facility

When the residents in a US district noticed greyish-green, slick and soapy water. Coming out of their taps. They contacted the local water corporation. Upon examination of the water samples, the water supply was found to contain a detergent solution. The authorities eventually traced the main back to a car wash facility.

As it turned out, a backflow situation caused the recycled wash rinse water at the car wash to reverse into the main supply line.  An employee at the car wash facility had connected a hose between the first rinse section of the car wash and the main water supply, accidently creating a cross connection.  Oblivious to the cross-connection, an employee turning a high-pressure pump which was used to pump recycled rinse water in the first stage of the wash. This caused the recycled water to be at a higher pressure than the main supply, thereby leading to a backpressure. The owner of the car wash facility installed a reduced pressure zone device at the boundary to prevent any future backflow incidents.

Backflow due to Carbonated Water

Almost every eatery has a soda machine. The machines combine flavored syrup with carbonated water, taken from the tap and mixed in with carbon dioxide, to make soda. The carbonated water contains a very week acid, carbonic acid, which is powerful enough to dissolve the copper supply lines. This is what happened at Mi Ranchito in Lenexa, Kansas. After 20 patrons of the restaurants reported being sick, the local authorities inspected the restaurant and found a back flow problem with the carbonated water lines. Copper poisoning led to vomiting, dizziness and sweating in people who had recently eaten at the restaurant. The only way to mitigate the issue was to install a dual check valve with an intermediate vent, upstream from a carbonating device and downstream from any copper in the water supply line.

Backflow At a Hospital

After a hospital at Michigan noticed rust-tasting water coming out of the water fountain, water authorities were informing. Upon further investigation, it was found that the rusty water was indeed blood mixing in with potable water supply. The source of the blood turning out to be a single autopsy table where a cross-connection had been establishing. Each table has a sink where blood and water that is using to wash organs and equipment, is collecting.

The tables also use a hose for the washing, connected to the main supply line. A pathologist accidently let the hose hang inside the sink in hurry since he couldn’t find any hook to hang the hose-spray unit. In the absence of a backflow preventer valve in the cross-connection between the supply line and the hose-unit, blood and other washing from the autopsy table back-siphonage into the main line and contaminated the water supply to the fountain.