I'm more curious how you use an Air Over Water Tanks AND a Bladder tank concurrently. The AoV tank already has air admittance devices.
Like Reach says, unless you have sulfur or iron in the water an air over water tank just adds several more items that fail often and require regular maintenance. The bleeder orifice, control check valve, Schrader valve, and air volume control are all temperamental and maintenance problems. None of these four things are needed with a bladder/diaphragm type tank set up. Then adding a bladder style tank after an air over water tank is like cross breading a horse and a giraffe. They are two different animals and are not made to work together.
Now for your 1.5 GPM explanation.
With two 119 gallon size pressure tanks and no CSV you have 60 gallons of draw down. A 1.5 GPM shower can run for 40 minutes before the pump will come on. During this entire 40 minutes the shower pressure will be decreasing from 60 all the way down to 40. When the pump starts at low pressure a 50 GPM pump will start hard at about 70 GPM. Then it will put 50 GPM into the two tanks that hold 60 gallons. The pump will run for just about one minute and shut off. It shuts off while pumping 50 GPM, so the check valve slams shut from wide open, causing water hammer and check valve failure. And the one minute of run time is not enough for the heat that was created during the hard start to dissipate before the motor shuts off. This process is repeated over and over no matter how much water you are using, unless you are using the entire 50 GPM the pump can produce.
With one 86 gallon size tank and a CSV3B2T we only have 20 gallons of water in the tank. With 1.5 GPM being used the pump will not come on for 13 minutes. When the pump is started the CSV is in the 5 GPM position. This makes for a mechanical soft start that greatly reduces the duration of the inrush current. As soon as the pump starts the CSV, which is set at 55 PSI goes wide open and lets the tank fill at 50 GPM until it gets to 55 PSI. The tank will be filled to 55 PSI in about 20 seconds and the CSV closed down to the 5 GPM position again. It would regulate 55 PSI constant and keep the pump running continuously if using more than 5 GPM. But when using only 1.5 GPM, 5 GPM is still coming through the CSV. 1.5 GPM is going to the shower and 3.5 GPM is filling the last 5 gallons of the pressure tank. This will take 1.5 minutes on top of the 20 seconds it took to get the tank filled to 55 PSI. So, you will get almost two minute of run time using the CSV, even with a much smaller tank. And during this two minutes of run time the CSV has restricted the pump to 5 GPM and the amps are reduce by 30-50%. With reduced amps the motor doesn't require as much run time to dissipate the heat created at start up, yet the CSV gives another minute anyway. This way the motor is sufficiently cooled before shutting down. Plus stopping the pump while the CSV restricts it to 5 GPM gives a mechanical soft stop. At 5 GPM the check valve is only open the thickness of a piece of paper, the check valve doesn't slam shut, and water hammer is eliminated.
But I think 1.5 GPM flow will be much more unusual than using more than 5 GPM. When using more than 5 GPM there is no comparison between the CSV and absolutely no cycling and a system without a CSV that will be banging off and on over and over as long as any water is being used. If you want to figure worst case scenario try using 10 to 40 GPM for extended periods of time. This is more common use of a pump this size and is why the CSV is a much better option. But like I say, most people have to replace a tank or three and be out of water a couple days at a time waiting for the pump to be replaced before they start to see the benefits of a CSV.
i have no doubt that we will be purchasing a device. I just don’t know how many pumps we will go through before they agree with what I believe to be a real solution...a better way.