LOL, and submersible motors run cooler when installed in a large body of water as compared to tight casing, right? Wrong!
Even 18% is insignificant on lightly used systems where the pump only cycles maybe 20 times per day. The CSV with the small tank would only cause 24 cycles per day. Saving 4 extra cycles per day is not worth the added expense, space, and heat required for a larger tank. If the water system is used enough that a big pressure tank would cause more than 20 cycles per day, a CSV would greatly reduce the number of cycles.
I am not missing anything. LOL How many gallons a day do you think are used for glasses of water, pots of coffee, washing toothbrushes, even flushing toilets? Lets pick a big number like 30 gallons. Even if the pump cycled for every gallon you use like this, which it won’t, that would still only be 30 cycles per day. It only takes a couple of long showers where the CSV doesn’t let the pump cycle at all, to more than make up for the cycling from intermittent uses of water.
That is exactly the point. “Most folks do other things with water”. And you have no idea what they are going to do with their water. So you just have to put in a system that will let them do anything they want with the water, and that is exactly what a CSV does.
Since you have no outside or long term uses of water you can certainly get by with a so-called “properly sized” pressure tank and no CSV. You just won’t get the benefit of strong constant pressure in the shower, or the reduced space and cost of the smaller tank. Also with the larger tank, the water will have been sitting in a rubber bag getting warm for hours before you use it, instead of being fresh and cool from the well as with the CSV and small tank.
There are lots of other benefits for using a CSV as well. Some pump installers don’t
think you deserve the benefits of a CSV system. Since you have a lightly used water system, you should just be happy with the pump cycling and the pressure swinging from 40 to 60 while you are taking a shower. You should also just be happy with the cost and space it takes for a big pressure tank.
Having constant 50 PSI for as long as you want to shower is a luxury that you don’t deserve. You might start enjoying longer showers or using water in other ways, and that would just be a waste of water. The CSV will also cause your pump and tank to last longer than normal, and that just isn’t being fair to the people in the pump industry.
Pump guys hate it when you say, “I was reading on the Internet”. Until the Internet, they never had to justify anything they said or did. Now most of their customers are better informed than they are.