A pressure tank is a tank with a diaphragm between a precharged air pressure chamber and the water being pumped into your water system. When the pump cycle starts the tank starts filling with water as the air in the chamber is compressed and the air pressure in the tank increases. When the water fills the tank to the point the air pressure reaches the cut-out pressure of the pressure switch on the system, the pump will shut off. The air pressure will then push the water out of the tank maintaining pressure until the tank is drained of water and the air pressure reaches the cut-in pressure of the pressure switch. Then the pump will come on to repeat the cycle. Installing a proper sized tank will limit the number of on/off cycles and quick cycling to protect and prolong the life of the pump while maintaining pressure flow.
What is the reason for a pressure tank on a water well pump system?
There are four main reasons for a pressure tank to be installed on your system. First, to extend and protect the life of the pump by reducing the number of on/off cycles. Second, to have a reserve capacity of water available for peak flow demands. Third, to have water under pressure available for use between pump cycles. And fourth to decrease system maintenance and help supply a constant flow of water.
How do I select the right pressure tank for my system?
To determine the correct size of pressure tank for your system there are three factors to consider. These factors are the pump flow in gallons per minute, the desired run time of the pump and the cut-in and cut-out settings of the pressure switch. Most pump manufacturers recommend a minimum run time of one minute with a preferred run time of two minutes to protect the pump and pump motor. The larger the tank the fewer the pump cycles resulting in longer pump life. So with this in mind the larger the tank the better but for the minimum tank size use this formula. Pump flow rate multiplied by the desired run time equals the required tank draw down capacity. An example of this, pump flow rate 10 gallons per minute x run time of 1.5 minutes = 15 gallons of draw down. Check the chart from the tank manufacturer for draw down ratings on their tank based on pressure settings. Draw down is usually about one third of the tank size so in our example the tank would be a 45 gallon tank.
What should the air pressure in the pressuretank be set at?
The air pressure in the tank should be set at two psi below the set cut-in pressure of the pressure switch on the pump system. It is important to note that this pressure needs to be checked and set with the pump system shut down and zero psi pressure in the water system or a false reading will result because of the water pressure against the diaphragm in the tank.
How can I be sure of proper tank sizing?
It's as simple as ABC. Contact ABC and let us size your tank or guide you through the sizing steps.