The Jones family bought a nice two and a half bath home. They are both in their early 60's. so they need a softener and call around for prices. The Acme Water Co. comes in and seeing as it's just the two people with no kids, he sells them equipment based on what he calculates will be their average water use. A couple years down the road Mr. Jones drops dead of a massive stroke and Mrs. Jones sells the house to the Smith family. The Smith family has 4 kids, 2 of which are teenagers. The smith families water use is 3 times the Jones use. Suddenly the softener is way undersized. That's why we have codes and yes, I do follow them.