What should follow after the heat source is turned off when draining a water heater?

After the heat source of a water heater is turned off, opening the highest level faucets is an essential step in the draining procedure. When the heater is turned off, the water inside it is no longer being heated. To facilitate the drainage of the tank, it is important to allow air to enter the system. By opening the highest level faucets, air replaces the water that is being drained, which helps to create a smooth flow and prevents any vacuum from forming within the heater.

This action enhances the effectiveness of draining the tank by ensuring that water can freely exit without being impeded by trapped air. In essence, it's about creating a pathway for both water and air to move efficiently during the draining process. This ensures that the water heater can be fully drained without residual water or pressure issues that might complicate maintenance or repairs.

In contrast, other steps like opening a pressure relief valve or loosening the lowest connection do not directly assist in the smooth drainage process in the same way that opening the highest faucets does. Closing all faucets would hinder the flow of air and impede efficient drainage, so it is not a suitable action to take following the heat source being turned off.