Cross-connection and Backflow Prevention

• Backflow is the reverse flow of water or other substances into the treated drinking water distribution system. There are two types of backflow: back-pressure and back-siphonage.
• Back-pressure happens when the pressure of the contaminant source exceeds the positive pressure in the water distribution main. An example would be when a drinking water supply main connects to a hot water boiler system that is not protected by an approved and functioning backflow preventer. If the pressure in the boiler system increases to where it exceeds the pressure in the water distribution system, backflow from the boiler to the drinking water supply system may occur.
• Back-siphonage is caused by negative pressure (vacuum or partial vacuum) in the water distribution system. This situation is similar in effect to sipping water through a straw. In the drinking water distribution system, negative pressure (back-siphonage) occurs during a water main break or when a hydrant is used for firefighting.

A physical connection between drinkable water and a liquid or gas could make the water unsafe to drink. Whenever there is a cross-connection, there is a potential threat to public health from the liquid or gas contaminants.

For example:

• Garden hose: Backflow through cross-connections can happen by leaving a garden hose turned on and submerged in a container of water or other liquid. That material could siphon back into the drinkable water supply.
• Private well: Backflow can also occur if an untreated water supply pump, like a private well, is connected to the drinkable water supply. Untreated water could accidentally make its way into the drinkable water of a home and the public water system.
• Lawn sprinkler system: TCEQ regulations require that all lawn sprinkler systems be connected through a mechanical backflow prevention assembly. Without one, stagnant water from the sprinkler system could go back into a home water system.

Backflow may affect the quality of the drinking water in homes, businesses or facilities. It can create health hazards if contaminated water enters the public water and is used for drinking, cooking or bathing.

Backflow events frequently occur, although most do not create health hazards. Unprotected cross-connections with water supply plumbing or public drinking water piping systems are prohibited. Everyone is responsible for protecting the public water supply from backflow that may contaminate our drinking water. It includes complying with the plumbing code and avoiding unprotected cross-connections.

The responsibility for preventing backflow occurrences is divided. State and local plumbing inspectors have authority over plumbing systems within buildings. In contrast, state regulatory agencies and public water suppliers regulate the protection of the distribution system at each service connection. Water customers have the ultimate responsibility for properly maintaining their plumbing systems. It is the customer’s responsibility to ensure that unprotected cross-connections are not created and that any required backflow prevention devices are tested following state requirements and maintained in operable conditions.

Preventing backflow situations in your home and business

• Be aware of cross-connections, and take action to eliminate or isolate them
• Do not submerge hoses or place them where they could become submerged in water or chemicals.
• Use hose bib vacuum breakers on fixtures (hose connections in the basement, laundry room, and outside faucets/spigots).
• Install approved backflow prevention devices on lawn irrigation systems and fire sprinkler system services. Determined the type of preventive devices required based on the potential type of pollutants or contaminants - high, low or moderate. In low-hazard situations, installing a residential dual-check device might be allowed.

Unprotected cross-connections or improperly installed assemblies should be retrofitted to comply with the state law and local plumbing codes (30 TAC Chapter 290), regardless of the building's condition.

On the supply side, federal law requires water suppliers or water companies, such as Brownsville Public Utilities Board, to protect their drinking water systems from contamination or pollution from backflow by cross-connections.