We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is a Double Check Valve?

By Paul Scott
Updated May 17, 2024
Our promise to you
About Mechanics is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At About Mechanics, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A double check valve is a plumbing fitting that prevents back siphonage to protect fresh water supplies from contamination. This fitting is typically installed on fresh water supplies for garden irrigation, combi-boiler, and fire suppression feeds where a backflow contamination risk exists. The unit consists of two standard backflow check valves mounted in series in a single housing. The basic concepts behind these valves include redundancy and the more reliable seating of each valve. Larger industrial type double check valves often include an isolation valve on either end and test cocks at various points while residential examples are typically sleek, in-line designs.

Back siphonage or backflow is a major source of fresh water contamination and has been positively linked with many waterborne disease outbreaks. Backflow contamination risks exist wherever fresh drinking water supplies are used to feed fire sprinkler systems, garden or agricultural irrigation, chemical dosing installations, or combination boilers. If no backflow protection is fitted to these setups, any significant drop in fresh side pressure will see contaminated water siphoning back into the potable supply. The best way of protecting fresh water supplies against this backflow is the installation of a backflow prevention device such as a double check valve.

A check valve is a fairly simple, robust, and reliable one-way valve that relies on a spring or gravity loaded plunger or a diaphragm to allow fluids to flow in one direction only. This is typically achieved by constructing the valve in such a way that the valve disc opens when exposed to pressure from one side and is forced closed positively should that pressure drop or be reversed. The double check valve features two such units mounted in series with the water flow path. The concept behind this design is a two-fold combination of redundancy and efficiency.

The redundancy benefits of the double check valve are pretty self explanatory; one valve is always being able to back the other up in the case of a blockage or mechanism failure. From an efficiency perspective, the pressure differential across the two valves during operation means that both are able to seat more effectively, thus boosting the overall efficacy of the system. The flexibility of the double check valve is further enhanced by the inclusion of dual shutoff valves on either end of the fitting which allow either side of the circuit to be isolated should the need arise. These and smaller test cocks used to test the functioning of the system are generally found on larger industrial variants. Domestic double check valves are generally smaller and more simple and are typically in-line designs or are incorporated into standard faucets or bibs.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.

About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.