Cross-Connection & Backflow Prevention

Backflow refers to the flow of water or other substances in the opposite direction of the treated drinking water distribution system. Two types of backflow exist:

Back-Pressure

• Occurs when pressure from the source of contaminants is higher than the positive pressure in the water distribution system
• Example: If a drinking water supply main links to an unprotected hot water boiler system, the pressure in the boiler system may surpass that of the water distribution system, causing backflow

Back-Siphonage

• Occurs when negative pressure (vacuum or partial vacuum) exists in the water distribution system, like sipping water through a straw
• Can happen during a water main break or when a hydrant is used for firefighting

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

Common Examples:

Garden Hose

• Can occur when a garden hose is left on and submerged in a container of water or other liquid, which could then be siphoned back into the drinkable water supply

Private Well

• Backflow can happen when an untreated water supply pump, such as a private well, is connected to the drinkable water supply
• Could result in untreated water accidentally entering a home's drinkable water and the public water system

Lawn Sprinkler System

• According to TCEQ regulations, all lawn sprinkler systems must have a mechanical backflow prevention assembly
• Failure to comply may result in stagnant water from the sprinkler system flowing back into the home water system

Backflow may affect the drinking water quality 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.

Preventing backflow occurrences is a shared responsibility:

State and Local Plumbing Inspectors

• Have jurisdiction over plumbing systems inside buildings

State Regulatory Agencies and Public Water Suppliers

• Oversee safeguarding the distribution system at each service connection

Water Customers

• Carry the responsibility of maintaining their plumbing systems
• Must ensure unprotected cross-connections do not arise
• Must ensure any necessary backflow prevention devices are tested in compliance with state regulations and kept in working order

Preventing Backflow in Your Home or 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 (basement hose connections, laundry room, outside faucets/spigots)
• Install approved backflow prevention devices on lawn irrigation systems and fire sprinkler system services