Questions about TDS, scum and foam

[Sjde]

Shouldn't a hot tub filter get the yellow scum?

If my TDS is well under 1500, should I still change the water after 3-4 months.

Besides adding to the TDS, what problems might you get if Foam Down is overused?

 

[JoyfulNoise]

Dimethicone is a organosilicon compound (polydimethylsiloxane or PDMS). It’s basically a chemically inert substance that stops foaming but doesn’t actually get rid of the thing causing your foaming issues.

Your hot tub, if I remember correctly, is in a rental home and is used by multiple guests/renters throughout the year. Therefore, for your own safety and that of your renters, you should be changing the water and purging the tub at least every 3 months. Hot tubs can be a major source of disease transmission and since you don’t know the exact health status of every guest bathing in it, you need to be extra careful otherwise your tub can become a breeding ground for disease.