Good discussion guys! 2HP and smaller pumps only need 1 GPM to stay cool. So the CSV1A and the CSV125-1 have 1 GPM minimums, fill the tank at 1 GPM, and keep the pressure constant and the pump running continuously when using more than 1 GPM. The small tanks (4.5 or 10 gallon size) only hold 1.2 and 2.4 gallons of water respectively. So yes the pup will come on when you flush a 1.6 gallon flusher. But the CSV keeps the pump from cycling on/off for showers, and everything else you use water for. So it doesn't hurt to add back a cycle for every toilet flush, as the total cycles will still be much less. Although it really doesn't add a cycle for every toilet flush, just every water use event. So when you flush and wash your hands, step into the shower, or someone elsewhere in the house is using water at the same time, there is no extra cycle for a single flush.
3HP and larger pump need 3-5 GPM to stay cool. So the CSV125-3 has a 3 GPM minimum, fill the tank at 3 GPM, and keeps the pump running when using more than 3 GPM.
The CSV3B2T has a 5 GPM minimum, which is recommended to keep a 5HP or larger pump/motor cool. It will fill the tank at 5 GPM, and keep the pump running when using more than 5 GPM. When using less than 5 GPM, like with a 3 GPM shower, the CSV makes the pump act like a 5 GPM pump working with a pressure tank. We would recommend a minimum of a 44 gallon size tank with 10 gallons draw. When using a 3 GPM shower the tank will supply the water for 3 minutes, the pump comes on and 2 GPM goes into the tank as the other 3 GPM is being uses for the shower. 2 GPM will fill the tank in about 3 minutes. So the pump will be on for 3 minutes and off for 3 minutes, worst case. If you up size to an 86 gallon tank, we set it to still take 3 minutes to fill, but it will double the off time to 6-7 minutes. 3 minutes on and 7 minutes off is about right when using 3 GPM in the house.
I am glad the VFD's are getting less expensive and more reliable, as constant pressure is a wonderful thing. VFD's were not cheap and didn't last very long when I was using them 30+ years ago. But even so a VFD is going to be more expensive and less reliable than a simple mechanical valve, like the CSV. Just don't fall for the hype that VFD's save energy, because they do not. Then it is a no brainer which is the least expensive and most reliable way to get constant pressure from your pump system. The CSV was designed to mimic the constant pressure performance and replace troublesome and expensive VFD's.