The simplest solution is to get a tank with a real volume that is 3 to 6 times the GPM capacity of your pump, with the ratio depending on horsepower of the pump.Originally Posted by cschippnick
Check the pump curve or run a test. If you have a pump that delivers 10 GPM at 50 psi, and you want your pressure switch settings at 40 and 60 psi, then you should have a minimum 30 gallon tank if your pump is 1 HP or less, and a 60 gallon minimum if your pump is greater than 1 HP. Those numbers are satisfactory, and larger is not a problem.
That will give you about 1 minute of pumping time for the 1 HP pump and about 2 minutes of pumping time for the larger pump.
You can read all of the arguments about smaller tanks and CSVs. A case can be made for using a CSV with a submersible pump, but I would never put one on a jet pump system because the jet pump already does about all that a CSV can do for you. A jet pump is so inefficient, and usually has so little pressure margin, that I believe that a CSV degrades a jet pump system.