Backflows do not occur under normal conditions, where your drainage and plumbing systems in buildings are in good working order, and your home or building provides a consistent water supply, even without a backflow preventer.

This is because the water pressure alone would be strong enough to keep the water still or flowing in one direction through your pipe network.

Incidents such as breakage in the main water line or using a fire hydrant might lessen the water pressure in your home or building. When water pressure is low or non-existent, water flows backwards into the municipal lines rather than forwards into your home and fixtures.

As a result of the negative pressure, pollutants such as fertilizers, soap, chlorine and human waste can be sucked back into the public drinking supply without a backflow preventer.

Contamination generally occurs through a lack of cross-connection control or connections between two water systems, one drinkable and the other not. Here are some frequent instances of home cross-connections:

  • Garden hose linked to the hose bib, with the other end in contact with a non-potable water source (e.g. a pool, puddle, or bucket)
  • Makeup water in the boiler that includes oil and rust, hence non-potable and harmful if ingested
  • Directly linked to the sanitary sewer water conditioning equipment
  • Older bathtubs with the tub spout located beneath the flood rim

Importance of Water Backflow Preventer

Backflow is created by the plumbing system’s back pressure or, in some cases, back-siphoning. Backflow is not an issue if the water is clean. However, if the returned water contains germs or chemicals, it might create a hazardous or unhealthy scenario.

In the case of a sprinkler system, you may be utilizing weed killer, fertilizer, and other lawn care products. Your water system may mistakenly pull such contaminants into your local water supplies if there is no backflow preventer on the sprinkler system cut-in.

importance of backflow preventers in commercial plumbing


A backflow prevention device is put in your home’s or building’s water pipes to guarantee that water flows in only one way and never the contrary. These devices safeguard potable water sources against pollution caused by various cross-connections, ensuring that drinking water is safe and clean for everyone.

If you want to understand more about backflow preventers, how they operate, and what they’re normally used for, you’ve come to the right spot!

backflow preventers usages

How does it Work?

A backflow preventer is a simple yet smart design. The architecture of the backflow prevention device is just like the heart valve in the human heart in that it enables water to flow in one direction and then closes when pressure is applied. It operates straightforwardly.

Water is siphoned via a branch line when it is drawn through the “main” line in your water system, such as when you turn on the kitchen faucet, start a load of laundry, or flush the toilet. During this procedure, the water transports whatever is in line with it.

how backflow preventers work

Different Types of Backflow Preventers

There are several varieties of backflow preventers, each with its mechanism and application. A professional plumber will be capable of advising you on the best kind for your property and inform you about the residential plumbing codes of your area that, as the property owner, you should be aware of them.

However, reliable residential plumbers always follow the rules and make sure they provide services to complete the project smoothly.

types of backflow prevention devices

This section will discuss the many types of backflow preventers, how they function, and where you can normally locate them.

1. Air gap backflow preventer

Unlike other forms of backflow preventers, an air gap is mechanical. For sinks and bathtubs, an air gap may be produced solely by positioning the faucet high enough above the flood lip of the sink or tub. An air gap device is employed when this technique can’t be applied.

Water softeners and dishwashers frequently use air gap devices. The air gap, achieved by correct fixture placement or by utilizing a device, creates a physical barrier between the water supplies and the non-potable water container.

2. Hose bib vacuum breaker

As the name implies, a hose bib vacuum breaker is often used for outside faucets where a hose attaches. This threaded device may be fastened into the faucet and stops backflow with its singular spring-loaded check valve.

Hose bib vacuum breaker

The valve opens and shuts in response to water pressure, enabling water to flow only one way and preventing back-siphonage of non-potable water (for example, from a pool, puddle, or pail of soapy water) through the hose’s end.

3. Atmospheric Vacuum Breaker

Usually made of brass and bent at a 90-degree angle, the atmospheric vacuum breaker (AVB) is a safety device.

A poppet valve is located inside an AVB and kept up and out of the way by typical water pressure. Air cannot get in at this point. But if the pressure drops and backflow are about to occur, the poppet valve drops and shuts off the line.

Atmospheric Vacuum Breaker

Air is also allowed into the system in conjunction with this action to stop any back-siphonage. These devices cannot be deployed in an environment where air contaminants should not enter the water since they operate according to atmospheric principles.

Another drawback of this technology is that the protected line, which is the potable water line, must be located upstream from the non-potable water source. Irrigation systems are the most typical application for these types of valves.

4. Pressure vacuum breaker

Pressure vacuum breakers (PVBs) work in a similar way as AVBs. The distinction, though, is that PVBs contain a spring-loaded poppet valve. Because of this distinction, PVBs can be put in systems where the potable water line (the line that’s protected) is downstream from the non-potable local water source.

Pressure vacuum breaker

These devices often have test cocks with calibrated gauges connected to ensure correct operation. The most prevalent application for PVBs is to prevent backflow in underground sprinkler systems.

5. Double check valve

Two spring-loaded check valves arranged in a sequence make up a double-check valve, also known as a double-check assembly (DCA). One of the key advantages of having a backflow preventer like this one is that even if one valve malfunctions, the other can still function because the two valves work independently.

Double check valve

In addition, while both valves are open, closing the first one lowers the pressure differential across the other valve, creating a tighter and more dependable seal against backflows. Preventing backflow in fire sprinkler systems is the most typical application for DCAs.

6. Reduced pressure zone device

A reduced pressure zone device (RZPD) is used particularly to stop health risks. Two separately operating spring-loaded check valves are included with RZPDs. The “zone,” a pressure-monitored chamber, is between these two valves. A differential pressure relief valve maintains the pressure in this zone. If both check valves malfunction, this third valve will let air into the system. Like double-check valves, the two independent valves can replace one another if the other fails.

Reduced pressure zone device

Signs of a Broken Backflow Preventer

Here we will discuss some signs that your current broken backflow valve might be malfunctioning and need repair or replacement.

Discoloured water

If your shower or sink water is hazy or discoloured, your water pipes likely have a damaged backflow preventer. Despite the temptation to dismiss the yellow or brown water, it’s crucial to contact a qualified plumber to prevent health problems. Consuming unclean water might result in symptoms including nausea, diarrhea, digestive issues, stomach aches, or dehydration.

Discolored water in plumbing system

Water leaks from the backflow preventer

Thermal expansion, dirt, or a change in water pressure are all potential causes of water leaks. The backflow preventer is damaged if it leaks water. It’s crucial to contact a licensed plumber to examine and replace the preventer to avoid flooding problems and water damage.

Slow drainage

If your bathtub’s water level rises while the sink runs, your backflow preventer valve may be broken. Once a pipe’s backflow valve is damaged, water becomes trapped and improperly circulates. This problem will result in water backups that could push through other home appliances, drains, and sinks. Additionally, a bad valve can cause your sinks in the kitchen or bathroom to drain slowly.


It is advised to have a backflow prevention assembly installed in situations where backflow will cause considerable harm since it can reliably and efficiently stop back pressure and back-siphonage. This device’s secure construction makes it suited for securing drinking water. Most commercial plumbing systems must also have a backflow preventer installed.