Types of Backflow Preventers

Searching for the right type of backflow preventer for your home? A backflow preventer is an important part of any home plumbing system – without one harmful backflow can contaminate your water supply. There are a few main types and styles of valves – each with its own benefits and features.

In this article we will teach you everything you need to know about the different types of backflow preventers

Type of ValveTop Rated Valve
Atmospheric Vacuum BreakerOrbit Atmospheric Vacuum Breaker
Double Check ValveWilkins 34-350XL
Double Check Detector Assembly ValveWatts 757DCDA-OSYXPIV-CFM
Reduced Pressure Zone DeviceWilkins 34-975XL

There are four main types of backflow preventers – all four are very similar but have a few important differences in how they work.

The four most common types are:

  • Atmospheric Vacuum Breakers
  • Double Check Valves
  • Double Check Detector Assembly Valves
  • Reduced Pressure Zone Device
4 Types of Backflow Preventers

Atmospheric Vacuum Breakers

An Atmospheric Vacuum Breaker is a common type of backflow valve. They are elbow – or ‘L’ shaped – and work using an atmospheric vent to keep water from reenter the potable water supply.

They are usually made of brass and use pressure to close the entrance to the drain line when water is not draining. Two of the downsides of this type of valve is that is must be installed at least 6″ above the system and can’t be near air contaminants.

Top Rated Atmospheric Vacuum Breaker

Orbit Backflow Preventer

Our pick for our top-rated atmospheric valve is the Orbit Atmospheric Vacuum Breaker. This valve is designed for sprinkler systems and made of solid brass – so it can handle up to 150 PSI. It should not be used on hot water lines but installation is easy all you need is a few common tools.

Double Check Valves

Double check valves are a good option that provide extra protection from backflow. They use a ball valve that opens and closes as water passes through the valve.

A double check valve can be used to prevent back pressure and back siphonage.

Unlike more dependable valves like an RPZ valve – a double check valve should not be used on lines connected to the water supply since they are more prone to leaking. One advantage of this style of valve is that they can be installed underground and inline – which makes

Top Rated Double Check Valve

If you are currently shopping for a new or replacement double check valve we recommend the Wilkins 34-350XL. This valve is made of bronze – which means it can handle high PSI – and can attach to drain lines between .75″ and 2″.

The 34-350XL is compliant with ASSE, USC, CSA IAPMO and AWWA so it is approved by nearly every organization around the world to prevent back-siphonage and backflow water.

Double Check Detector Assembly Valves

Double check detector assembly valves offer additional protection from hazardus substances dangering your water system. Some top of the line models include special sensors that can report leaks and backflow in realtime.

This type of valve is much larger than the previous but houses two interior spring loaded check valves. They are normally installed on sprinkler lines or a fire protection system instead of an line attached to the public water system. The main benefit is that it prevent ‘black water’ from reentering the public water system. Two of the most popular brands are Watts and Wilkins.

What is Black Water?

Black water is stagnant water that has been sitting in water lines undisturbed. Over time this water will become totally black – and full of harmful bacteria that can cause help problems if it flows into the potable water system. An approved backflow prevention device and yearly inspections are required in many cities around the country.

Top Rated Double Check Detector Assembly

Our pick for the best double check detector assembly is the Watts 757DCDA-OSYXPIV-CFM. This valve is a top-of-the-line valve that provides total protection (unless there is a leak) from black water entering your water supply.

Like other Watts valves, this double check valve is highly reliable and comes with a built-in shutoff valve, post indicator valve, and cubic feet meter!

Reduced Pressure Zone Device

Reduced Pressure Zone Valves – aka RPZ devices – are the most dependable type of backflow prevention valve. This type of backflow preventer valve is installed in on the most important water lines where backflow protection is critical to protecting drinkable water from non potable water.

A reduce pressure backflow preventer works but creating a pressure difference inside the valve. Due to the difference in downstream pressure water is unable to flow the reverse direction. Once the water stops flowing the reduced pressure backlow preventer closes the outlet shutoff valve so there is no harm to the drinking water. A backflow device like an RPZ backflow preventer is required in many areas with water lines connected to city water source as well as regular inspections and testing.

Top Rated Reduced Pressure Zone Device

Wilkins 34

If you are in the market for a new reduced pressure zone assembly valve then we recommend the Wilkins 34-975XL. Like other valves, this pressure vacuum breaker is made of a brass interior and bronze exterior.

It uses a Wye design so it easily fits in tight spaces which makes it a good choice for basements and small closets. It protects against back siphonage and backflow that can carry harmful contamination into the water supply. Plus – this model is lead-free which is a requirement in some parts of the country.

What is the best type of backflow preventer?

One one of the most common questions we get asked is: what is the best backflor prevention valve? There is no one best ‘backflow assembly’ – the answer depends on your situation. RPZ valves and other similar mechanical backflow preventer valves offer the most protection from backflow – but also cost the most money! If you only need a valve attached to an irrigation system you can install a cheaper backflow prevention assembly like a Double Check Valve.