Sorta.
But mineral build-up is the real problem. Rinsing out your shampoo and conditioners with your regular water will not hurt. Chelators bind to the minerals so that they can be rinsed out, eliminating the chance of build up caused my using hard water (or relaxing with no-lye) over and over again.
I have hard water and I really don't need to chelate with every wash. I can go a few washes without it before I notice. I would say by the 4th wash, I would notice a need to use a chelating shampoo.
To avoid that I can do it with every or every other wash.
But, now I look to my conditioners as a solution. I notice that regular deep conditioning with conditioners that contain EDTA (chelator) really cuts down my need for a chelating shampoo. I normally only use the shampoo on relaxer days (I use no-lye) and when I use henna.
Lustrasilk Cholesterol (Olive oil or shea) and Joico K-Pak Intense Hydrator are my current deep conditioners and they call contain EDTA. I hardly ever use my Kenra Chelating shampoo anymore. Once a month at the most, and I have very hard water.