girl drinking pure water from a glass

Everything You Need to Know About Backflow

Why Do Most Landscape Irrigation Systems Need Backflow Prevention Devices?

irrigation installation When you turn on a faucet, the last thing you expect is to see worms swimming around in your bathtub.  Yet, according to an article by Mary Elizabeth Williams-Villano in the Irrigation & Green Industry Magazine, that happened to a Michigan homeowner who was sprinkling their lawn when a water main break caused nematodes to be sucked from their lawn into their domestic water supply.  A properly installed backflow prevention device, often called a backflow preventer, could have prevented this from happening.

In New York State, the Department of Public Health requires backflow prevention devices to be installed with any new landscape irrigation system supplied from a potable water source (e.g., public water or a well that is used for drinking and cooking water). An irrigation system that draws directly from a body of water (e.g., lake or pond) or a well that is not connected to a potable water supply, does not require a backflow prevention device.

Additionally, New York State requires that existing landscape irrigation systems installed without backflow prevention devices be retrofitted with one if they are connected to a potable water supply.What is Backflow?

Water supply lines are intended to flow in one direction only, but sometimes they don’t, and that’s when something called backflow happens. If water in an irrigation system flows back in – instead of flowing out – it will carry with it contamination from whatever was around the output source (e.g., drip line or sprinkler head that was turned on at the time the backflow event occurred).

Backflow can introduce a variety of harmful chemicals that are in your soil or in your sprinkler head mechanism (e.g., lawn fertilizers, weed killers, pesticides), insects, worms, and bacteria from decaying organic matter and animal waste that will contaminate your potable water supply as well as the local water supply, thereby imposing an unacceptable, and preventable health hazard.

How can backflow happen?

When exterior water supply lines are installed for an irrigation system, they create a cross-connection in the piping between outside water and inside (potable) water. Cross connections can lead to backflow when a loss of water pressure sucks water back into the supply line instead of allowing it to continue to flow out to the irrigation system. Water pressure loss is caused by ordinary fluctuations in demand, an activated fire hydrant, a water main break, or in the case of a well, a dry pump tank.

By having Irrigation Tech install a backflow preventer between the potable water supply and the automatic watering system supply, you can keep potable water safe from outside contaminants.

How does a backflow prevention device work?

A picture containing wall, indoor, dirty Description automatically generated While there are many different types of backflow prevention devices (backflow preventers), they all ensure that water flows only one way – the right way – from your main supply line to your irrigation system drip lines and sprinkler heads. When a drop in water pressure creates a reverse (sucking) pressure, the backflow prevention device valve closes shut to prevent water from flowing backward from your irrigation system and into your main water supply.

While all backflow preventers perform the same function, and in our northern climate are usually installed in a basement, how they do their job depends on the type of device selected to fit the specific needs of your property. For example, air gap devices use a simple mechanism in which vertical gaps allow for safe and regulated pressure fluctuations while anti-siphon valves, such as you might have on an outside hose faucet, use valves to stabilize the pressure when the water supply is shut off. If you want – or need – more security in backflow prevention, you can select a double-check device. Double check devices, which have two check valves to keep backflow from entering the supply line, are installed so that they are parallel to the pipes.

Some preventers – such as reduced pressure zone (RPZ) preventers required in 100-year flood pains, and pressure breaker vacuum assemblies – must be installed at least 12 inches above the ground to work properly. Double check valves have more flexibility and can usually be installed below grade in a basement. They can also be installed vertically. Other types of preventers cannot operate in a vertical position.

For most installations, water authorities require, or Irrigation Tech recommends, double check valve backflow preventers.

Does a backflow prevention device require regular maintenance or testing to ensure that it works properly?

backflow preventer The New York State Public Health Department and local water authorities require that a state-certified technician test your backflow prevention device annually. Irrigation Tech has state-certified technicians who can usually perform the New York State required annual inspection at same time they perform a system start-up, mid-season inspection, or winterization. Pairing a backflow test with other routine irrigation system maintenance is more convenient for you and costs less than a separate backflow test appointment.

To perform a backflow test, we remove test cocks from the backflow preventer and attach hoses connected to our test kit. We then take meter readings from the test kit to ensure that the check valves are working properly and record the readings on a report that we certify and file with the local water authority as evidence that your device was tested as required, and when required.

By following New York State’s inspection, testing, and reporting mandates, irrigation system users will never have to worry about contaminating their own or their community’s drinking water.


When it’s time to start-up, reset, inspect, repair, refurbish, upgrade, expand, replace, or winterize your lawn sprinkler system, turn to the professionals at Irrigation Tech in Pittsford, NY. Our team of irrigation experts has been installing and servicing high-quality residential and commercial systems throughout Monroe County and The Finger Lakes Region for nearly 40 years. We’re fully certified backflow prevention specialists who can perform NYS-required annual backflow tests and ensure you have access to the latest innovations in irrigation systems and quality installation. We’ve also been chosen by the Irrigation Association twice as one of the Top 100 Contractors in the country. To learn more about the Irrigation Tech team, visit our website or call (877) 8-IRRIGATE to speak with a customer service representative.