What is TDS?
TDS is Total Dissolved Solids.
Do We Care about TDS Levels in Pool Water?
TDS is not very important for pool care. It used to be a way to tell when water was "old", but that was before we were able to more accurately measure the components that make it up. Now it's just a relic of a bygone era.
We care about measuring and managing the individual chemicals but the Total Dissolved Solids is meaningless.