Ensuring the safety and purity of water in our plumbing and water supply systems is of the utmost importance. Devices such as the Double Check Backflow Preventer (DC), a crucial tool in preventing water contamination, support this mission. This guide will explore the nuances of DCs, including their parts, applications, installation procedures, and the various types available, including those designed for fire protection systems.
Understanding Double Check Backflow Preventers
A Double Check Backflow Preventer is ingeniously designed to stop polluted (non-health hazard) water from reversing into the clean water supply. It achieves this through two independent check valves arranged sequentially, which act together to prevent any backward flow of water. DCs have two resilient seated shut-off valve and four resilient seated test cocks. DCs are effective against two main hazards: backpressure and back-siphonage, making them versatile in a wide range of situations.
Key Components
- Check Valves: At the core of the DC are two check valves that permit water flow in only one direction. If the flow direction changes, polluted water will be blocked from re-entering the clean water system.
- Test Cocks and Shutoff Valves: Integral for the maintenance and testing of the DC, these components facilitate easy access for inspection and repair. Test cocks allow for connection to testing equipment, while shutoff valves enable isolation of the device for hassle-free servicing.
Applications of Double Check Backflow Preventer
DoubleCheck Backflow assemblies are designed to prevent the backflow of pollutants that could affect the aesthetic or non-health aspects of water quality, not substances that could cause illness or death if ingested.
- Backpressure: Occurs when the pressure on the downstream side overtakes the supply side pressure, potentially causing pollution.
- Backsiphonage: A condition where a drop in pressure in the supply line creates a vacuum, pulling polluted water back into the drinking water.
Installation Guide
The installation of a DC is a task that requires adherence to specific codes and standards. Here’s a basic overview of the process:
- Selecting the Proper Location: The device should be positioned to be easily accessed for service, protected from freezing temperatures, and placed before the connection to the non-potable source.
- Proper Orientation: DCs are generally designed for horizontal installation, but vertical models are also available. The flow direction indicated on the device must be followed.
- Testing and Commissioning: Post-installation, it’s essential to perform pressure tests to verify that the device functions correctly under various scenarios. This step typically requires specialized knowledge and equipment.
Types of Double Check Backflow Devices
While the standard DC is widely used, there are specific models designed for particular applications, including:
- Fire Backflow Preventers: These are specialized for fire suppression systems, ensuring that chemicals used in fire suppression do not contaminate the public water supply. There are two more backflow devices similar to the DC, and they are the Double Check Detector Assembly (DCDA) and the Double Check Detector Assembly-Type II (DCDA-II). These assemblies are for fire sprinkler systems and can detect unauthorized use of water or leaks. There is a larger DC assembly with a smaller assembly connected to the larger assembly. The design of this device is for flows of 2 GPM or less to only pass through the smaller assembly. For the DCDA, the smaller assembly is another DC; the inlet is connected to the larger assembly on the upstream side of the #1 Check Valve, and the outlet is connected to the downstream side of the #2 Check Valve. The DCDA-II has a smaller assembly that has only one check valve, and the inlet is connected to the larger RP on the upstream side of the #2 Check Valve, and the outlet of the smaller assembly is connected on the downstream side of the #2 Check Valve
- Compact and Vertical Models: These models provide flexibility and efficiency for situations where space is limited or a specific installation orientation is required.
Conclusion
Double Check Backflow Preventers are indispensable in protecting our water supplies from pollution due to backflow. With a clear understanding of their function, installation, and the available types, stakeholders in plumbing, irrigation, industrial processes, and fire suppression can ensure that water remains safe and unpolluted for all.
