Who Determines High Hazard Classifications for Backflow Cross-Connections?

You would think one agency sets the rules for backflow protection. It doesn't; there's no single authority telling plumbers, civil engineers and water suppliers exactly what's acceptable and what isn't.

Instead, the hazard level at a possible cross-connection decides which backflow preventer is recommended or required. Reduced pressure zone (RPZ) assemblies are the go-to solution for high hazard classification. The harder question is who dictates the hazard level for each building type, line type and possible scenario.

Plenty of voices weigh in, all of them working to protect public health and safety, and their standards vary. From the outside, most people assume the EPA has the final say on which backflow protection device is required, as well as when and where. Its cross-connection control guides are the only federally distributed manual on the subject, yet they do little to define what makes a hazard high or low.

The 2003 and 2006 guides (the most current versions) defer that call to the water supplier stating that, “The supplier of water should have the right of entry to determine degree of hazard and the existence of cross-connections in order to protect the potable water system.”

So water systems determine the hazard, what does that mean for customers across different municipalities?

Backflow Preventer Options for Different Hazard Levels

Different backflow preventers provide different levels of protection, and their hazard levels depend on the substances involved.

• Low hazards are pollutants and do not pose a health hazard
• High hazards are considered contaminants and would pose a health hazard

The most commonly referenced backflow devices are double check (DC) backflow valves and reduced pressure zone (RPZ) assemblies. (This article explains the differences between DC and RPZ valves.) There are also air gaps, vacuum breakers, anti-siphon fill valves and dual checks. Each device is best suited for certain applications and types of backflow.

Air gaps, atmospheric vacuum breakers, pressure vacuum breakers and reduced pressure zone assemblies are all acceptable even for high hazard situations, but only for back-siphonage backflow.

The RP and RPDA are the only devices that should be used when there is a risk of high hazard back-pressure backflow. Backpressure occurs when the customer's water pressure is higher than the public supply's pressure. This can happen if a customer has various pumps, has elevated piping such as in a high rise or uses pressurized containers.

What Influences Hazard Levels

Suppliers look for three common hazards when setting a hazard level: line use, building use and future possibilities. Here's how each one factors in.

1. Line Use

Sometimes determining hazard level is as simple as considering what will be present in the line that needs protection.

In general, irrigation systems are high hazard and require an RPZ device, because they can come into contact with fertilizer, pesticides and animal waste. Different equipment carries different risks, so certain devices are paired with them based on hazard level.

Beverage dispensers typically have dual checks, dishwashers mostly use atmospheric vacuum breakers and lavatories are often paired with air gaps.

Fire protection lines get more complicated. The type of fire protection helps determine hazard, since there are deluge systems, dry pipe systems and systems using chemical fire retardants. The other main consideration for fire sprinkler lines comes down to future possibilities.

2. Building Use

Any building where materials are used that would pose a health threat — contaminants — requires a backflow device suited for high hazards.

Some are obvious: chemical plants, manufacturing plants and oil and gas production warehouses. Medical buildings including clinics, morgues and hospitals are high hazard too, along with restaurants and laundromats.

The list of buildings that could introduce contaminants into the water supply is long, and exposure to the public community is what drives the classification. Some of these buildings will do just fine with air gaps or vacuum breakers at individual pieces of equipment. Others will need RPZ valves after the meter for containment backflow prevention. Some engineers would recommend both, but containment and isolation is another discussion entirely.

Many buildings, regardless of use, are at risk of backpressure backflow and would require an RPZ device. High rise buildings, buildings with sprinkler systems for fire protection, and even boilers and water heaters can cause backpressure.

3. Future Possibilities

It's difficult for public water system staff to anticipate what might happen to each of their thousands of water lines for residents and businesses. That's why water suppliers must think about the possibilities before the initial backflow protection is chosen and installed.

Here are some common accounts:

• Buildings change hands and get updated over the years. A clothing store may close and a new restaurant could open in the same space, turning a low hazard building into a high hazard one. Would the restaurateur know they needed a new backflow device? Would it have been better to plan ahead and provide a higher level of protection in the first place?
• Handy business owners may alter their piping configurations, add a hose to the end of a sink's spout or install a new irrigation system. Each scenario could cause a change in hazard or introduce an entirely new cross-connection at the property. The combination of reactions between introduced substances and the potable supply are exactly what these classifications guard against.
• Most fire protection lines only require a low hazard level backflow preventer — a double check detector assembly. But an owner may add fire retardant chemicals without the water supplier's knowledge, or operate a dry pipe system as a wet pipe system without identifying the associated risks.

Recommendations for Determining Hazard Levels for Your Installation

Because there's no end-all ruling coming down from the EPA and federal government, other associations publish their own cross-connection control manuals with guidelines and recommendations for analyzing hazard levels.

1. The USC FCCCHR has a Manual of Cross-Connection Control, Tenth Edition, for sale on its website. The manual covers a range of topics to help you run a successful cross-connection control program.
2. The American Water Works Association also sells a cross-connection control manual, most recently published in 2024. It outlines actual and potential cross-connections, discusses the different backflow preventers available for protection, and offers specific recommendations for lines and buildings regarding hazard levels.
3. Each water district has its own standards for determining hazards. It may follow one of the recommendations above, or it may have developed stricter or looser rules for its system. Frequency of inspection and testing may vary from one system to the next as well.

These rules are sometimes difficult to find. They're often located online in the municipal code, standard details, or the cross-connection control section of a website, as is the case with Nashville, Tenn.

When the local determination points to a high hazard cross-connection, an RPZ assembly installed above grade in an ASSE 1060-compliant enclosure keeps the assembly testable and protected.