PG13,
I, respectfully, diasgree with the notion that there is no harm from the UV sanitizer. The UV it emits breaks down the chlorine in the water. The harm is that you pay for the chlorine and the electricity to run the UV unit.

If the pool is indoors or otherwise shielded from the sun's UV it may be necessary to run a UV unit to break down combined chlorine. If the pool is exposed to the sun it gets plenty.

Please don't think I'm swinging a wet noodle - I usually just float on them.