From that depth, a ¾ HP can deliver about 14 gallons at 60 PSI. Should be plenty unless all baths are being used at the same time. A CSV at 60 PSI would do the trick. With a large tank you still have to wait for the tank to drain from 70 to 50 before the pump will start, and then the CSV would hold at a steady 60 PSI as long as water is being used. You don’t have to wait as long for constant pressure if you use a smaller tank.
Ballvalve, you really should try a CSV so you can get over your phobia of “extended run timesâ€. With a big tank, you set the CSV just under the cut off setting, so it doesn’t take long to fill even a big tank. Ie; 60 PSI Cycle Stop Valve, use 43/63 pressure switch setting. This way the tank is almost full before the CSV starts topping it off at 1 GPM, and your run time is not that long. However, extending the run time some can be good for the pump. Pumps like to run and shorting the run time causes cycling.
Widening the bandwidth of the pressure switch, such as 52/85 or 60/90 will overstretch and shorten the life of the bladder in a tank. Then using a pressure regulator after the pressure tank still lets the pump cycle on and off while you are using water. This kind of defeats one of the purposes of constant pressure, which is to keep the pump from cycling itself to death. Plus using a regulator after the pressure switch means you are always seeing the low end of the pressure. Then of course bypassing the regulator so you can have high pressure on the irrigation, also means you have to be careful to run enough water to keep the pump from cycling. You don’t have to worry about how much or how little water you are using when you have a CSV.
