"I'm not sure what Valveman low pressure cutoff switch does for you, just one more part to fail... along with the pressure tank and CSV." Rancher
The low pressure cut off switch is a simple pressure switch that is commonly used on low producing wells. It will shut the pump off if your tank runs out of water, or if you have a major line break.
This switch will not fail any sooner than any other type of pressure switch.
The CSV is also dependable and is what keeps the pressure tank, pressure switch, pump, motor, capacitor, and everything else in a pump system from failing.
"Raucina's adjustable relief valve is the cheapest way to do what you want to do, Bob NH's system will also work cheaply." Rancher
Again.....A small pressure relief valve cannot be used to dump excess water back to the tank. It would pop open and closed to do so and would cause major water hammer. These small pressure relief valves are not modulating type valves. They dump and shut, not modulate evenly.
"My system will also work just fine, you didn't mention if you had kids that could mess with the system, just that you wanted to water the garden with the 400 gallons of rain water." Rancher
There is always something that can mess with a pump system. You should plan for the worst, and expect the best, instead of the other way around.
"The pump will work fine running continuously even with brief periods of a completely closed nozzle." Rancher
The operative word here is BRIEF. Just walk away for a few minutes and you pump is toast.
"Or... you could just raise the pressure cutoff of your existing switch so the pump will not cycle when you are in the spray mode of watering." Rancher
Ranchers first quote...."BTW you should never have a pressure switch without a pressure tank."
And he was right the first time!!!!!
themp... Yes the same size as an expansion tank, just make sure it doesn't have a tiny opening. I will attach a picture of one similar to this.