All You need to know about Dual Check Valve and
Dual Check with Atmospheric Port
What is Dual Check Valve?
The Dual Check Valve is a backflow preventer that is used to prevent both back-pressure and back-siphonage.
These have two independent check valves and are used for residential supply lines and fire sprinkler systems, post-mix beverage machines as well as tea and coffee machines.
What is Dual Check with Atmospheric Port
The Dual Check with Atmospheric Port, or the DCAP, is a backflow preventer that consists of two independently operating check valves that have an intermediate atmospheric port. The DCAPs are designed to protect against both back-siphonage and backpressure. Their applications include sterilizers, underground rainwater tanks, hairdressers, non-toxic boiler feed lines, and laboratory equipment installations. They are mainly used for low hazard applications only.
How does Dual Check with Atmospheric Port work?
In a DCAP, the vent valve is closed during the normal operation and the two check valves open, thereby allowing the flow of water through the unit. In the case of back-siphonage, both the check valves close and the atmospheric vent opens to allow air to enter the intermediate zone. Whereas, in case of back-pressure, if the second check valve does not close tightly for some reason, the leakage is vented to the atmosphere via the vent port.
In the case of backpressure condition, the dual check preventer forces the checks to close tighter due to an increase in the pressure. If the second check does not work, the first check acts as a backup to stop backpressure going through the device. In back-siphonage, a sub-atmospheric condition at the inlet causes the loading of the checks so that they close.
Features
The Dual Check Valve must be used only for non-health hazard cross-connections and for applications where there is a continuous pressure. It can be installed horizontally or vertically and are compatible with working in tight spaces.
The DCAP should be installed according to the accessibility for maintenance and testing of the device. It is highly suggested to maintain a 12’’ minimum clearance between the floor grade and DCAP. It cannot be installed in places where the port-based discharge is questionable.
How is it different from other Backflow Preventers?
A dual check valve is similar to a double check valve because it consists of two independently acting check valves that are spring-loaded. Both dual check valves and DCAP are used for low hazard applications. However, the dual check valves usually don’t include the shutoff valves. The proper selection of backflow preventer is very paramount to ensure adequate protection for the desired application. It is important to remember that different backflow preventers provide different levels of protection.
Why are Dual Check Valves and Dual Check with Atmospheric Port the best for Backflow Prevention?
Dual check valves do not need any special tools, crimping, glue, or soldering and have a faster install time. The ease of use of these valves reduces the risk of errors produced. They are quite versatile and are compatible with PEX, copper, HDPE, CPVC, etc. pipes.
Dual Check with Atmospheric Port is designed for low head loss and has a union for easy maintenance and installation. They are also available with solder connection and pip thread with an internal cone strainer for easy usage. Also, all the parts are temperature resistant making it suitable for both hot and cold water continuous pressure applications.
We use backflow preventer devices that meet the requirements laid out by the American Water Works Association (AWWA) Standard for Dual Check Valve(ASSE 1032, ANSI/ASSE 1024)and Dual Check with Atmospheric Port(ASSE 1012)and approved by labs sanctioned by the Conference of State Sanitary Engineers.
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