plumbing network. Pressure tanks are integral parts of rural water systems that use pumps to draw water from wells and lakes, but they’re also ideal as whole-house water hammer arrestors. The place where the main water pipe comes into your home is usually accessible, with lots of space available for the tank itself. A 5 or 8-gallon diaphragm tank is what you want. It includes an internal rubber membrane that separates the water from the air held within the top half of the tank. This air offers the cushioning action that will stop your water hammer. Without the diaphragm, the air in the tank would slowly disappear as it dissolves in the water.