When is a Backflow Preventer Required?

Backflow prevention assemblies are designed to prevent contaminated water from mixing into clean municipal water supplies, which are usually used as drinking water. Contaminants like sediments, bacteria, and fertilizer are a major public health hazard, so in New Jersey, there are regulations in place that require certain buildings to have backflow preventers installed.

What is “Backflow”?

Simply put, “backflow” means that water flows in the plumbing system have become reversed, causing potable water– clean water you can drink– to mix into the used water, which contains bacteria, chemicals, and other harmful contaminants.

Usually, water backflow results from one of two key processes: backpressure or backsiphonage.

  • Backpressure is a form of water backflow that results from an imbalance in water pressures. The downstream pressure is greater than upstream, or supply, pressure. Essentially, your home or building’s plumbing system contains water at greater pressures than the municipal water mains, which isn’t supposed to be the case. This pushes used wastewater from your plumbing system into the municipal water supply, potentially contaminating potable water. An example might be if you have a large water boiler that’s connected via plumbing with the potable water supply. Without a backflow prevention assembly, high pressure in the boiler could push dirty water into the clean water, contaminating it with sediment and other materials that could make it unsuitable for drinking.
  • Backsiphonage results from negative pressure, creating a partial vacuum effect. The systems distributing the water fall behind in the system using the water, in terms of water pressures. As a result, a siphoning effect moves contaminated water in the wrong direction. This can happen during a water main break, or in an emergency when a nearby fire hydrant is used (which involves high water pressures).

Water Backflow Prevention Requirements

Backflow is a major environmental and health threat, because it allows contaminants like sediments, bacteria, and chemicals to mix into clean drinking water supplies. Because of this, most places, including New Jersey, have legislation in place that requires a backflow prevention device for certain homes and buildings. These devices stop backflow from occurring, protecting municipal drinking water supplies.

Backflow preventers are commonly installed in buildings where clean water cross-connects with any of the following installations:

  • Large boilers. A large boiler can present a backflow hazard when the pressure inside gets too high, pushing the dirty water inside back up into the clean water system.
  • Irrigation systems. This includes extensive lawn sprinkler systems. Backflow from irrigation systems is hazardous because of the presence of fertilizers and lawn chemicals such as pesticides.
  • Fire suppression systems. Fire suppression systems can also create pressure differences and siphoning effects that can lead to backflow.

Here in New Jersey, backflow prevention requirements are outlined in the New Jersey Clean Water Act, a piece of legislation last amended in 2011. Special provisions and standards are outlined for the design and testing of backflow prevention devices in buildings with physical connections between public water facilities and potentially contaminated water sources. Backflow devices must be approved and meet the appropriate requirements, and backflow prevention valve installation and testing must be done by a certified professional.

Do I Need to Install a Backflow Prevention Assembly at my Home?

Backflow prevention devices are most common in commercial settings, but some residences may also need one. One of the most common reasons for a residential backflow preventer installation is a home sprinkler system that cross-connects with the drinking water system.

If something happens that causes a drop in pressure in the water mains, such as the use of a nearby fire hydrant or a burst pipe, contaminants can flow back through the sprinkler head because of the pressure difference. This can introduce fertilizers and pesticides into potable water.

If your sprinklers are only connected to irrigation water via a ditch system, you probably don’t need a backflow valve. However, you’ll need one if it connects to drinking water supplies.

Backflow Preventer Installation

Codes and legislation require backflow prevention assemblies to be approved and to be installed by an approved and certified contractor. Some types of backflow risks, such as irrigation systems with chemicals, require different types of backflow valves than other applications. To find out more, call us today at Backflow Testing NJ.


Do you have ongoing sewer backflow issues from the city street to your house? basement? business? sewer slop that requires sewer line repair  might need sewer backflow valve install

Our experienced, licensed contractors can talk to you about the type of backflow prevention you need to keep your home, and the city’s clean water supplies, safe from contamination. To find out more, call us at 201-399-2160.