Again, I'm not the pro here. I'll explain how I understand it. I'll take my situation for example. I have an 82 gallon pressure tank with a 25 gallon draw down. When my pressure tank is full (and my pressure switch is 40/60) and I turn on a water spicket, after I have drained the pressure tank to a pressure of 40 lbs, my jet pump comes on, at that time the CSV is wide open allowing the maximum water volume through it. I'm still watering my trees or taking a shower or whatever and the pump is running and the CSV is going all out.
Let's say I am taking a shower with a shower head is rated at 2 gpm. I have my CSV set at 58 psi. Once my pump pushes the pressure to 58 psi, the CSV will begin to regulate the pressure at 1 gpm so that the pump will continue to run as long as I'm taking my shower because my shower head is calling for 2 gpm. As soon as my shower is done and all other water usage is off, the CSV allows the pump to fill the pressure tank at 1 GPM until the pressure switch reaches 60 psi and turns off the pump. This takes about 3 minutes. I have a pressure tank that is too big as far as I'm concerned but with the CSV it still works.
Once my big bladder tank finally gives up the ghost, I will go to a small pressure tank with a draw down of less than 5 gallons that way my pump will come on quicker but will also turn off quicker and I will reset my pressure closer to 50 lbs instead of 58 lbs. I love the fact that the CSV is mechanical and not electrical like a VFD pump. Again, I'm a novice and probably even a neophyte, but I've done alot of reading and question asking from other forums besides this one and the CSV is one of the best choices for longevity of your pump, pressure tank, pressure switch and all components because your pump is cycling less. It's too bad that most people that have wells and pumps don't know how valuable the CSV is. What's even more sad is that pump and well companies don't know about it or simply don't buy into it because it won't make them money.