Central Well & Pump Service provides two types of pressure tanks that are used in well pump systems. There are air over water tanks and pre-charged bladder or diaphragm tanks. Air over water tanks are hollow tanks that you can manually charge with air periodically.
A bladder tank or diaphragm tank will have a bladder or diaphragm that will hold a pre-charged amount of air physically separated from the water in the tank.
A pre-charged tank is much more reliable and convenient than the old air over water tanks as they do not need periodic maintenance and are much more reliable. Pre-charged tanks are available in steel construction and in fiberglass construction for corrosive water.
A pressure tank serves two purposes; one, to hold a reservoir of water for readily available use and two, to ensure that the well pump does not short cycle, which extends the life of your well pump.
The size of tank determines how much water it will hold in reserve and what your pump's cycle time will be. For example, a typical 119-gallon pressure tank will hold 35 gallons of water. In this case, the home will be able to use that 35 gallons before the pressure switch will call for water. Assuming the home has a ten gallon per minute well pump when it is called upon to fill that 119-gallon tank it's cycling time will be 35 divided by 10 which is 3.5 minutes. This is important because well pumps should have a minimum of two minute cycle time to avoid premature failure. Because cycle time plays such an important role in the lifespan of your well pump system bigger is always better and in some applications, we recommend installations of multiple pressure tanks.