GROCO Pressure Storage Tank - 0.5 Gallon DrawdownPressure Storage Tank 0. 5 Gallon Drawdown A pneumatic pressure charge, matched to the pump cut on pressure prevents water logging by separating the air charge from system water pressure with a rubber bladder. The result is smooth pressure delivery, even temperature mix in showers, and reduced pump cycling. Tanks may be mounted in any position, and anywhere in the cold water plumbing after the pump. PST tanks may be used for fresh or salt water. Mount