Types of Pressure Tanks
There are two types of pressure tanks used in well pump systems -- air over water tanks and pre-charged bladder or diaphragm tanks. Air over water tanks are hollow tanks that you periodically manually charge with air. Bladder tanks or diaphragm tanks have a bladder or diaphragm that holds a pre-charged amount of air physically separated from the water in the tank. Pre-charged tanks are more reliable and convenient than air over water tanks as they do not need periodic maintenance and are available in steel construction.
What is a Pressure Tank For
A pressure tank serves two purposes -- to hold a reservoir of water for readily available use and to ensure that the well pump does not short cycle. The size of the tank determines the volume of the reserve and the cycle time of the pump. For example, a typical 119 gallon pressure tank will hold 35 gallons of water. The home will be able to use the 35 gallons of water before the pressure switch will alert for more water. If the home has a ten gallon per minute well pump, it’s cycle time will be 3.5 minutes when called upon to fill the 119 gallon tank. Well pumps should have a minimum 2 minute cycle time to avoid premature failure. Cycle time plays an important role in the life span of your well pump system and in some scenarios, we will recommend installations of multiple pressure tanks.