Since expansion tanks in the heating system are necessary not only to compensate for the changing volume of water but also to replenish minor hot-water leaks, a certain amount of water, called the operating volume, is provided in the expansion tank. In the calculation algorithm given above, the operational volume of water is laid down in the amount of 3% of the capacity of the heating system.

For over 60 years, Mid-West Instrument has been a leading provider of premium differential pressure gauges. Need help finding the right pressure gauge and equipment for your business? Reach out to us today to speak with one of our experienced professionals.

The opening point of a PVB is typically set by the manufacturer and is determined based on the spring tension of the air inlet valve and the design specifications of the check valve. It is crucial that the PVB opens at the right moment—when the system pressure falls just below atmospheric pressure—to ensure it fulfills its protective role without unnecessarily interrupting the water flow during normal operation. Advanced testing equipment, including digital backflow test kits like the Model 855 equipped with the MachBackflow app, enables precise measurement and verification of the PVB’s opening point, ensuring compliance with regulatory standards and optimal performance.

Pressure Vacuum Breakers (PVBs) are critical components in preventing backflow and protecting water supplies from contamination due to back siphonage. Understanding the opening point of a Pressure Vacuum Breaker is essential for ensuring it functions correctly to protect potable water systems. The opening point of a PVB is a key performance metric that determines the effectiveness and reliability of the backflow preventer under varying conditions.

2. The first sign of an incorrectly calculated expansion tank or its incomplete adjustment is when the safety valve often trips.

Several challenges can affect the accurate determination and maintenance of the opening point in PVBs. Debris, wear, and tear, or even improper installation can cause the PVB not to open at the correct pressure, either failing to protect the water supply or causing unnecessary water system interruptions. Solutions include regular maintenance, cleaning, and calibration of the PVB, along with the replacement of parts like springs and seals as needed to ensure reliable operation.

Selection of an expansion tank should be performed taking into account its temperature characteristics and strength. The pressure and temperature at the point of connection of the tank should not exceed the maximum permissible values.

Standards set by agencies such as the American Water Works Association (AWWA) and the Environmental Protection Agency (EPA) guide the installation, testing, and maintenance of PVBs. Regular testing is mandated to ensure that the opening point remains within acceptable limits, as drift from the specified setting can compromise the device’s effectiveness. Professional backflow prevention testers use calibrated instruments to measure the opening point during annual inspections or after any repairs or adjustments to the assembly.

Warning: Cancer and Reproductive Harm – www.P65Warnings.ca.gov For complete information on Proposition 65, please read this informational PDF or visit www.p65warnings.ca.gov

1. When using glycol mixtures as hot-water, it is recommended to choose an expansion tank with a volume that is 50% larger than the calculated one.

We are gathering a community of experts in the design, installation, and service of heating, hot water, and water supply systems in Australia. Join the community and you will receive emails with requests for work in Australia from our visitors.

Digital advancements, such as the integration of apps and digital test kits, have greatly improved the efficiency and accuracy of testing PVBs. These tools allow for real-time data collection and analysis, facilitating immediate adjustments and providing a comprehensive database of test results for ongoing monitoring and compliance purposes.

A Pressure Vacuum Breaker comprises a spring-loaded check valve that closes when water flows at a normal rate through the system and an air inlet valve that opens when internal pressure drops below atmospheric pressure. The opening point of a PVB refers to the specific pressure at which the air inlet valve opens to admit air into the system, preventing a vacuum from forming and thereby stopping any back siphonage. This function is critical in maintaining the safety and integrity of drinking water systems, especially in areas where sudden drops in water pressure can occur, leading to potential backflow of contaminants.

The volume of the expansion tank must be greater than or equal to the volume obtained as a result of the calculation. There are no negative consequences from overestimating the volume, beyond the calculated one.

In conclusion, the opening point of Pressure Vacuum Breakers is a critical parameter that ensures these devices function as intended to protect water supplies from contamination due to back siphonage. Accurate determination and maintenance of the opening point are essential for the effective operation of PVBs. With the aid of modern technology and regular testing, water safety professionals can ensure that these crucial devices continue to operate reliably, safeguarding public health and complying with regulatory standards.

If the installation of expansion tanks is planned indoors, it should be taken into account that tanks with a diameter of more than 750 mm and a height of more than 1.5 m may not pass through the door, and mechanization means will be needed to move them. In this case, it is better to prefer not one, but several membrane tanks of smaller capacity.

Technology plays a pivotal role in enhancing the testing and maintenance of Pressure Vacuum Breakers. The development of apps like MachBackflow, which can be paired with digital test kits, allows for streamlined data management, including recording the opening point of PVBs. These technological solutions not only improve the accuracy of tests but also significantly reduce the time required for testing and documentation, thereby enhancing the overall efficiency of backflow prevention programs.

The method of calculating expansion tanks is complex and routine, but in general, the following relationships can be established between the volume of the tank and the parameters affecting it:

Calculation of an expansion tank is performed to determine its volume, the minimum diameter of the connecting pipeline, the initial pressure of the gas space, and the initial operating pressure in the heating system.

« Mid-West® Instrument’s Model 855 Digital Backflow Test Kit Powered by the MachBackflow AppPressure Gauge Connection Bushings in “Bellows Type” High Accuracy Gauges »