Like other states in the nation, Nevada has requirements and regulations that monitor the public water systems to ensure they are safe. Clean water is essential to daily life. Backflow prevention regulations in the state serve to protect the potable water supply.
Backflow is the undesired reverse flow of used water back into the public water supply. Backflow prevention devices are required on all industrial and commercial properties, including irrigation systems. They are also needed in many multi-family residential units.
Nevada Laws & Requirements for Irrigation Backflow Devices
The regulations related to irrigation backflow devices and preventers for the state of Nevada contain several laws. These laws are in the State’s Environmental Commission’s R049-18 and Nevada Administrative Code 445A. Section 23 of this regulation states that:
Except as otherwise provided in section 4 of this regulation, each service connection must have an assembly for the prevention of backflow, of a type that is commensurate with the degree of hazard that exists on the property of the customer of a public water system. Except as otherwise provided in AC 445A.67185 to 445A.67255, inclusive, and section 4 of this regulation, the assembly may consist of any one of the following, as listed in the order of least to most protection:
- A double-check valve assembly
- A reduced pressure principle assembly
- An air gap
Section 4 of the regulation provides that a fire hydrant directly connected to certain water mains does not require an assembly to prevent backflow unless the water supplier determines that the lack of such an assembly presents a degree of hazard to the public water system. In all other instances, an irrigation backflow device or backflow preventer is required.
How Do Irrigation Backflow Preventers Work?
When water enters a building, it is supposed to only flow in one direction – into the building. However, due to pressure changes in the pipes, it’s possible that water can flow backward. When it occurs, it can re-enter the main water supply lines. The most common backflow causes happen when a break in the main water line or a fire hydrant is used. Because a reduced pressure zone develops during these events, water is no longer pushed forward and can flow backward.
Unfortunately, when backflow occurs, it can contaminate the water with the following:
- Fertilizers and pesticides
- Human waste
- Chlorine from pools and spas
- Soap from sinks, dishwashers, and showers
Contamination of this type ruins the potable water supply. Backflow prevention systems function as one-way gates. These systems allow water to flow into buildings but stop when it flows backward. There are several types of backflow prevention systems.
Atmospheric Vacuum Breakers
Atmospheric vacuum breakers rely on air pressure to function rather than water pressure. An air inlet valve remains closed when water moves in the proper direction. If the flow reverses, the air inlet valve opens to prevent back-siphonage. There are several limitations to this type of backflow preventer. They are less reliable than other systems. They can also be costly since they require a vacuum breaker after every control valve on a pipe or sprinkler zone. In addition to these factors, atmospheric vacuum breakers do not protect against chemigation backflow. This type of backflow can occur when chemical pesticides or fertilizers are used with irrigation water.
Pressure Vacuum Breakers
A pressure vacuum breaker assembly is one of the most common backflow preventers. It is easy to maintain and repair. There are several parts to these systems, including:
- An inlet shutoff valve and valve body. These components house a pressure vacuum breaker.
- Test valves.
- Spring-loaded check valves that close when water flow stops.
- An outlet shutoff valve
This assembly also has an air inlet valve. This valve opens when internal pressure is higher than external pressure to prevent back-siphonage. Unfortunately, these systems only work to prevent back-siphonage. They cannot stop the back pressure if the pressure is too high. They are also unable to prevent chemigation backflow.
There are also spill-resistant vacuum breakers. They operate similarly to pressure vacuum breakers but contain an additional diaphragm. This diaphragm seals the system to keep water from spilling out of the air inlet when the assembly becomes pressurized.
Double Check Valves
Double-check valve systems are also standard for indoor and outdoor systems and underground or in-line use. They contain an inlet shutoff valve and a valve body with two spring-loaded check valves, four test valves, and an outlet shutoff valve. The check valves operate independently. These systems can protect from both back-siphonage and backpressure. Unfortunately, they cannot prevent chemigation backflow.
Reduced Pressure Principle Backflow Assembly
Also referred to as a reduced pressure zone assembly, these are considered the safest and most dependable backflow preventers. They are generally more expensive and require more maintenance and installation work. These systems have several components, including:
- An inlet shutoff valve
- A pressure differential release valve. This valve separates into two independent spring-loaded check valves, four test valves, and an outlet shutoff valve.
- A mechanically independent relief valve to maintain a low-pressure zone between the check valves.
This backflow prevention assembly can be added to many plumbing configurations. Unlike other irrigation backflow devices, they can protect from chemigation backflow.
Selecting the Right Irrigation Backflow Device or Prevention Assembly
There are many factors to consider when selecting the right irrigation backflow device to meet your needs. Users must consider their existing or planned plumbing system and the full range of coverage required. Cost and the installation and maintenance complexity are also considerations to keep in mind. And any property owner will want to select something that complies with Nevada state laws and regulations.
Legacy Fire can help customers understand all the options available for irrigation backflow prevention. We can also help our clients understand the benefits and drawbacks of each device. This process ensures you will select the one most compatible with your needs.