Safer Water

Let's Work Together For Safe Water

Public health officials have always been concerned about cross connections and backflow in plumbing systems and in public drinking water supply distribution systems. People have utmost confidence in the water they drink. Open a faucet and we drink what comes out. If, however, the water is contaminated, sickness and even death can be the result. Community awareness can greatly reduce the chance for cross connections and backflow incidences.

Cross-Connection and Backflow Defined

A cross-connection is a direct or indirect connection between a potable water system and any other liquid, gas, or other substance. A direct connection is a physical link between the piping arrangements of a potable and non-potable system. An indirect connection is where the water itself makes the connection such as a hose from a potable supply submerged in contaminated water, or a leaking pipe that "pools" water around the break.

Backflow is the unwanted reverse flow of water, gases or other substances into a potable water supply distribution system. It can potentially occur at any time there is a cross connection between the potable supply and any source of pollution or contamination.

Sources of contamination and how you can be affected.

Examples of likely contamination sources are wash basins, sinks, dishwashers, garbage disposals, showers, bathtubs, toilets, and hose bibbs (faucet to which a hose may be attached or buried yard hydrants).

Cross connections and unwanted backflow have serious health implications. Many cases have been documented tracing serious disease outbreaks directly to a specific cross-connection and backflow condition in a potable system. These cases have been particularly prevalent for underground sprinkler systems, submerged hoses, and at or near commercial facilities with high-hazard non-potable uses such as hospitals and industrial sites. Although major disease outbreaks get plenty of publicity, it is likely many backflow events occur in small systems and go unnoticed. This is because too few people may be affected to create a public stir, or persons who become ill may just think they have the flu.

What you can do to prevent cross-connections in your home.

Point-of-use backflow preventers are the best way to protect the water you drink everyday. There are many types of approved backflow preventers. The three most used by the general public include the: Air gap, Atmospheric vacuum breaker (AVB), and the Pressure vacuum breaker assembly (PVB), Each backflow preventer type described in this section is designated as a method, a device, or an assembly. Specific criteria apply to each.


An air gap is a method for backflow prevention that is considered the ultimate backflow preventer, although it is relatively easy to circumvent in unmonitored situations. An air gap should be used whenever appropriate, before any other type of preventer is considered. An air gap is defined as the physical separation between a potable and non-potable system by an air space. The best example of this is the standard design of all types of sinks where there is a separation between the free-flowing discharge of the faucet and the overflow rim of the receiving basin. (pictured at right)


An atmospheric vacuum breaker (AVB) is a device consisting of a body, a checking seat, and an atmospheric vent. During normal operation, potable water seals off the vent. If a negative pressure develops in the supply line the check valve drops to seal the opening while the vent opens to admit air to break the vacuum.

A hose bibb vacuum breaker (HBVB) is a type of AVB (pictured right). The HBVB is a device with a metal body, a springloaded check valve, and air inlets. It is one of the simplest and cheapest ways of preventing low and high hazard back-siphonage through hoses attached to threaded connections. These can and should be installed on all threaded connections, sill cocks, and yard hydrants where there is any possibility a hose will be attached for any purpose. HBVBs are available with a means to manually drain the device for freezing conditions. Click here to see the HU approved HBVB.


A pressure vacuum breaker assembly (PVB) is an assembly consisting of a loaded air inlet valve, an internally loaded check valve, two properly located test cocks, and two isolation valves. PVBs are suitable for low and high hazard back-siphonage installations, the same as AVBs. Unlike AVBs, PVBs may have valves downstream and be under continuous pressure. Typical installations include swimming pools, heat exchangers, degreasers and livestock water systems. They are most often used in sprinkler irrigation systems with downstream control valves (pictured at right).

For more information on how to prevent cross-connections contact the Hastings Utilities Water Department by calling (402) 463-1371 or