6 Best Double Check Valves for Backflow Prevention

You leave a hose in the stock tank overnight, and a power outage causes the well pump to lose pressure. Suddenly, dirty trough water is siphoning back towards your house, contaminating the same water your family drinks. This isn’t a far-fetched scenario; it’s a real risk called backflow, and it can turn your clean water supply into a health hazard. A reliable double check valve assembly is your first and best line of defense.

Disclosure: As an Amazon Associate, this site earns from qualifying purchases. Thank you!

Protecting Your Water with a Double Check Valve

A double check valve assembly (DCVA) is essentially a one-way gate for your water. It contains two independent, spring-loaded check valves that work in tandem. Water can flow forward from your main supply, but if the pressure drops, those valves slam shut, preventing anything from flowing backward.

This isn’t the same as a simple, cheap check valve you might screw onto the end of a hose. A DCVA is a robust, testable device designed for permanent installation where the risk of contamination is present but considered non-health-hazard. Think of irrigation lines feeding a garden, a water supply line to a barn, or a system for filling livestock waterers. It protects your potable water from things like dirt, sediment, and animal waste that might get siphoned back.

It’s crucial to understand that a DCVA is for low-hazard situations. If you’re connecting a line to a chemical sprayer or a system with potent fertilizers, you need a higher level of protection, like a Reduced Pressure Zone (RPZ) assembly. But for the vast majority of cross-connections on a small farm, a quality DCVA is the right tool for the job, providing reliable protection without the complexity and maintenance of an RPZ.

Watts 007M1: The Reliable Farm Workhorse

When you need a backflow preventer that just plain works, the Watts 007 series is the old standby. It’s built from cast iron, it’s heavy, and it’s been the industry standard for decades for a reason. Think of it as the trusty farm truck of DCVAs—not fancy, but it will never let you down.

The biggest advantage of the Watts 007 is its ubiquity. Parts are readily available at almost any plumbing supply house, and any professional you hire will know exactly how to test and service it. The internal components are straightforward, making repairs a manageable task if you’re comfortable with basic plumbing. It’s designed for a long service life under continuous pressure.

The main tradeoff is its bulk and weight, especially in larger sizes. The cast iron body, while durable, is susceptible to rust over the long term if the protective coating is compromised. It’s best suited for installations where space isn’t a major constraint and you prioritize proven reliability over modern, lightweight designs.

Zurn Wilkins 350 for High-Hazard Protection

The Zurn Wilkins 350 is a step up in robust design and is often seen in commercial applications, which tells you something about its durability. While it’s still a double check valve for non-health hazard applications, its construction is exceptionally tough. This makes it a great choice for critical systems where you want an extra margin of safety and longevity.

What sets the 350 apart is its short lay length, meaning it takes up less horizontal space in the pipeline than many competitors. This can be a lifesaver in a crowded pump house or when retrofitting a system. It also features a single access cover for servicing both check valves, simplifying maintenance.

This is the valve you choose when you’re installing a system you don’t want to think about again for a very long time. It’s a bit more of an investment upfront, but its build quality and design for continuous pressure applications provide peace of mind. It’s overkill for a simple garden hose bib, but perfect for the main supply line branching off to your barn and fields.

Apollo 4A Series: Durable Bronze Construction

If your water is aggressive—high in minerals, acidic, or drawn from a well—the Apollo 4A series is an excellent choice. Its main body is constructed from lead-free bronze, which offers superior corrosion resistance compared to the coated cast iron found in many other models. This is a valve built to last in less-than-ideal water conditions.

The Apollo valves are known for their modular, replaceable check valve cartridges. This makes servicing incredibly fast and simple. You don’t have to rebuild the checks with tiny springs and seals; you just unscrew the old cartridge and pop in a new one. For the busy hobby farmer, that time saved is invaluable.

The bronze construction means a higher initial cost. However, you have to weigh that against the potential cost and hassle of replacing a corroded cast iron valve in five or ten years. If you’ve ever had to fight with rusted bolts on old plumbing, you’ll immediately appreciate the long-term value of a bronze body.

Febco 850: Compact Design for Tight Spaces

Sometimes, the biggest challenge isn’t flow rate or pressure; it’s simply space. The Febco 850 shines in these situations. It’s one of the most compact and lightweight DCVAs on the market, making it the go-to solution for installations inside valve boxes, tight utility closets, or crowded mechanical rooms.

Febco achieved this small footprint by using a composite check valve system and a very efficient body design. Despite its size, it doesn’t compromise on performance and meets all the necessary safety standards. It’s a clever piece of engineering for modern, space-constrained plumbing.

The tradeoff for its compact nature is that servicing can feel a little more cramped. There’s just less room to get your hands and tools in there. However, for a new installation where you can plan your layout, or a retrofit where no other valve will fit, the Febco 850 is the undisputed problem-solver.

Conbraco DCV 4A: Top-Entry for Easy Service

The Conbraco (now Apollo) DCV 4A series has one feature that makes it a favorite for anyone who does their own maintenance: top-entry access. A single, large access cover on the top of the valve allows you to get to all the internal components without ever removing the valve body from the pipeline.

This is a massive advantage. On other models, major service can require cutting pipe and sweating new fittings. With the DCV 4A, you just shut off the water, unbolt the lid, and lift out the check valve modules. You can clean, repair, or replace the checks in a matter of minutes and be back up and running.

This ease of service makes it a fantastic choice for any long-term installation. You know that eventually, every valve will need maintenance. Choosing one that makes that job as painless as possible is a smart move that pays dividends down the road, saving you time, frustration, and potentially the cost of a plumber’s visit.

Ames Colt C200: Lightweight, Low-Pressure Loss

For irrigation systems, every pound of pressure matters. The Ames Colt C200 is specifically designed for low head loss, meaning it creates very little friction and won’t significantly reduce the water pressure downstream. If you’re trying to push water over a long distance or operate pressure-sensitive sprinklers, this is a critical feature.

The C200 uses a lightweight, corrosion-resistant ductile iron body, making it much easier to handle and install than traditional cast iron models, especially in larger 2-inch or 3-inch sizes. A single person can often manage an installation that might require two people with a heavier valve. This is a real back-saver.

This valve is the performance choice. It’s ideal for the main line of an irrigation system where you need to preserve as much pressure as possible for your drip lines or sprinklers. The combination of low pressure loss and manageable weight makes it a top contender for any application where hydraulic efficiency is a priority.

Choosing and Installing Your Farm’s DCVA

Picking the right DCVA isn’t about finding the "best" one, but the right one for your specific job. Before you buy, ask yourself a few key questions:

• Where will it live? If it’s in a tight valve box, the compact Febco 850 is your answer. If it’s out in the open, the heavy-duty Watts 007 is a great fit.
• What is my water quality? For corrosive well water, the bronze Apollo 4A is a smart long-term investment to prevent premature failure.
• Who will service it? If you plan to do your own maintenance, the top-entry Conbraco DCV 4A will make your life much easier.
• Is water pressure critical? For a long irrigation run, the low head loss of the Ames C200 will ensure your sprinklers at the far end get the pressure they need.

When it comes time to install, always follow the manufacturer’s instructions. Most DCVAs must be installed horizontally to function correctly. Make sure to install isolation ball valves before and after the DCVA so you can shut off the water for testing and service. And most importantly, check your local plumbing codes. Some jurisdictions have very specific requirements for backflow prevention, and it’s always better to get it right the first time.

Your water source is the lifeblood of your farm and your home. Protecting it isn’t a place to cut corners. Investing in a durable, well-chosen double check valve assembly is a fundamental step in building a safe and resilient water system that will serve you reliably for years to come.

Frequently Asked Questions (FAQs)

What is a double check valve backflow preventer?

A double check valve backflow preventer is a plumbing assembly featuring two independent spring-loaded check valves designed to stop contaminated water from flowing backward into clean water supplies. This device includes four test cocks and two shutoff valves for annual maintenance and testing. Plumbers typically install it on low-to-medium hazard systems such as residential fire sprinklers and dedicated lawn lines where toxic chemicals are not present.

What does a double check valve do in an irrigation system?

Double check valves in irrigation systems prevent stagnant water, fertilizer runoff, and soil bacteria from siphoning into household drinking lines during sudden pressure drops. If water main pressure drops below the sprinkler line pressure, the two internal springs close tight within milliseconds. This mechanical barrier holds back dirty standing water from sprinkler heads, maintaining safe municipal water quality without needing continuous outdoor drainage lines.

How do I test a double check valve for backflow prevention?

Testing a double check valve requires a certified backflow technician to measure differential pressure across both internal check valves using a specialized three-valve or five-valve test kit. The technician connects differential pressure gauges to the assembly’s test cocks, checks that check valve one holds at least 1.0 psi, and verifies check valve two holds tightly. Local water authorities usually mandate submitting these official test results within 30 to 60 days of the inspection date.

How much does it cost to install a double check backflow preventer?

Installing a double check valve backflow preventer typically costs between $300 and $900 for residential lines, including parts and professional labor. The valve unit itself ranges from $100 to $400 for standard 3/4-inch to 2-inch pipe sizes from brands like Watts or Apollo. Labor adds another $200 to $500 depending on pipe access, trenching needs, and local permit fees. Larger commercial systems can easily exceed $1,500.

What is the difference between a double check valve and an RPZ backflow preventer?

Reduced pressure zone (RPZ) backflow preventers provide higher hazard protection than double check valves by including a hydraulic relief valve between the two checks that dumps water during failures. Double check assemblies are rated only for low-hazard applications and contain trapped water without an open relief port. Consequently, municipal codes require RPZ units for toxic risks like chemical feeds or commercial boilers, whereas double check valves are permitted underground or inside basements.

Why is water leaking from my double check valve test cocks?

Water leaking from double check valve test cocks usually indicates loose internal screws, worn rubber seals, or debris stuck inside the small ball valve mechanism. Mineral scale and sediment flushed through pipes often lodge in the miniature test ports. To fix a minor drip, use a flathead screwdriver to open and flush the port for two seconds before tightening it shut. If dripping persists, replace the threaded test cock adapter.

How often does a double check backflow valve need replacement?

Most double check backflow preventer assemblies last between 10 and 20 years before the entire cast brass or bronze body needs complete replacement. Internal components such as rubber discs, O-rings, and stainless steel springs wear out faster and require rebuilding every 3 to 5 years. Routine annual testing identifies degraded rubber discs before the unit fails, allowing plumbers to install inexpensive rebuild kits rather than replacing the entire valve.

Is a double check valve legal for high-hazard commercial drinking water lines?

Plumbing codes prohibit using a double check valve for high-hazard commercial connections where backflow would introduce toxic chemicals, industrial waste, or dangerous pathogens into drinking water. National and local standards, including the Uniform Plumbing Code, require a reduced pressure zone assembly for high-hazard risks like medical facilities, car washes, and chemical processing plants. Installing a double check valve in these settings violates municipal codes and risks heavy fines.