Actually a CSV can be just as important on a low producing well as a high producing well. A pressure tank is just another load for the pump to fill after it has been supplying water to the house. So I have seen many times that a low producing well would supply water to the house, then pump dry before the big pressure tank got full. You can still use a large pressure tank with a CSV is you want, and the CSV will refill the tank at 1 GPM, so the well doesn’t pump dry while filling the tank.
Big pressure tanks don’t really help much with low producing wells, because you can’t make sure the tank is full every time you start to use water. With a 40/60 pressure switch, the tank could be full and at 60 PSI, or it could be almost empty at 41 PSI, when you turn on a faucet. You have a 50-50 chance either way. And Murphy’s Law says it will always be at 41 PSI when you need water. Now not only does the pump have to supply water directly to the shower when needed, it has to refill the 25 gallons in the 80 gallon pressure tank, after you turn off the shower. So the tank is just an additional load on an already low producing well, that may not have 25 gallons remaining.
The CSV is one reason why large pressure tanks are getting cheaper, because they are not needed any longer. A $90 CSV and a $100 tank (not to big to ship) will do things that six large tanks can’t do, which is stop the pump from cycling. More or bigger tanks just slow down the cycling, they don’t stop it. I agree diaphragm tanks are better than bladder tanks, but even bladder tanks will last longer with a CSV, because the bladder is not (cycling) or being used very much.
I also prefer the Cycle Sensor to any of the pump savers available. For one thing they have proven to be more dependable. For another, other pump savers don’t work well with a CSV. When a 1 HP pump is working with a CSV, other pump savers see the amps drop from 9 to 5 amps, and thinks the well is dry, shutting off the pump. The CSV is what makes a 1 HP pump drop from 9 to 5 amps, the well is not dry. The Cycle Sensor can be adjusted to any amp setting, so when set at 4.5 amps, it knows the difference between low flow and no flow on the 1 HP pump.
I always used as large a tank as the customer could afford or that would fit, until I realized there is a better way. After an installer starts using Cycle Stop Valves, he soon realizes that almost every application can benefit from one.
Oh I still use 80 gallon pressure tanks. But only on bigger pumps with bigger CSV’s that produce between 1,000 and 5,000 GPM.