Massachusetts Plumbers Journeyman Practice Exam

Where should the vacuum relief valve be installed to protect water heaters and storage tanks from siphoning?

1. Below the tank

2. Above the heater

3. Within the tank

4. Above the tank

The correct answer is: Above the tank

The correct placement of the vacuum relief valve above the tank is essential for preventing siphoning, which can lead to potential damage or malfunction. By positioning the vacuum relief valve at this height, it allows the valve to effectively release any vacuum pressure that may form within the system. This ensures that the water heater or storage tank maintains safe operating conditions by preventing negative pressure that could lead to the impairment of the storage tank or other components. When the vacuum relief valve is installed above the tank, it is poised to activate at a height where it can detect the drop in pressure associated with siphoning situations. This strategic placement allows for proper venting of air into the system, thereby eliminating the risk of siphon-induced collapse. In terms of other placements, a valve installed below the tank would not be capable of responding effectively to the pressures that require relief, while a placement within the tank would not be able to adequately vent the vacuum situation that could occur. Similarly, an above-the-heater position—though it may seem plausible—may not be as effective as directly above the tank in ensuring complete protection against siphoning effects. Therefore, positioning the vacuum relief valve above the tank is the best practice for safety and performance.