What is the third step for taking a DPV out of service?

The correct step for taking a Double Check Valve Assembly (DPV) out of service is to crack open the main drain valve. This process is important as it allows any residual water in the system to drain out safely. By doing this, the pressure is relieved within the system, and it helps prevent any potential water hammer or other pressure-related issues while the DPV is out of service. Additionally, draining the system can reduce the risk of water spillage or flooding during maintenance or repairs.

In the context of servicing fire protection systems, ensuring that water can safely exit the system when making changes or performing maintenance is crucial for both safety and operational efficiency. This step is part of a systematic procedure to ensure that the system is safely and properly taken out of service without causing damage or safety hazards.