>> If you live anywhere with winter you will have to use two inline. If you live anywhere north of the Mexico I wouldn’t waste the money. <<
We live in south central WI and have never had a problem.
We pull water out of an 88 ft well next to the house.
A single unit works fine for the whole house.
That is good to know. Idaho isn’t so harsg and the only succesful installations I know of have two in line. I tried one to no avail and went back to the trusty old tank.