“When is it time to drain the hot tub?” I think this question hit the millionth-time mark in my pool-dude world.
First, while spa companies recommend quarterly drains, there’s some misinformation in that answer.
Barring no real problems with green water or some other nasty water issue, the only parameter to drain a hot tub is Total Dissolved Solids (TDS). End of story.
TDS measures all the solids that are in the tap water, not including what happens to hot tub water every time you use your spa. In other words, when you are in the hot tub at 104 degrees, that steam is distilled water–lacking any minerals–leaving the minerals behind in the water.
Think of your hot tub like a giant tea pot. When you use the hot tub and distill the water the TDS raises incrementally. When TDS reaches 1500 ppm that’s when it’s time to drain the hot tub.
Why? High TDS lessens the effect of your chemicals. That means disinfectants are less effective, as are all the other chemicals used. And when minerals fall out of solution your spa’s innards will look like the inside of your teapot. It’s okay for the teapot, but not for motors, pumps, heaters and plumbing. Think expensive repair bills.
When to drain your spa is not a time issue–not drain every 3 months, or whatever. It’s how many times you use your hot tub combined with the natural TDS of your tap water. And to complicate this issue is tap water TDS measurements can change weekly. From the same water spigot I’ve measured TDS at 500 ppm and then 900 ppm several weeks later.
High TDS symptoms: You can’t keep your chemicals in solution, no matter how much you add, your spa has no water quality, bad smells, etc.
You can purchase a TDS meter usually for under $25. I sell them for less. Yeah, that’s a blatant bit of self-promotion, but, hey, I’m just another pool dude trying to make a living ;-)!!! E-mail me at firstname.lastname@example.org