How often should you drain and refill a hot tub?
The short answer
For a tub that gets regular use. Sooner if it is used heavily, a little longer if it mostly sits covered.
Fresh water does more for a hot tub than any product. Over weeks of soaking, the water collects what sanitizer cannot remove, and it gets harder to keep clear and balanced. Draining resets it.
A year at one drain every three months.
What changes it
- How many people soak, and how often. This matters most. Four people every evening wears water out several times faster than two people on weekends.
- The size of the tub. A small tub has less water to share the load.
- How you sanitize. Follow the interval your system's maker gives; some ask for a fresh fill on their own schedule.
A quick rule of thumb
A 450-gallon tub with 2 people a day: 450 ÷ 3 ÷ 2 is 75 days, about two and a half months. One "soaker" is one soak of about 20 minutes.
The rule assumes the water is kept balanced and sanitized in between. Use it together with the calendar: if it gives you a much longer gap than four months, drain at four months anyway.
Signs it is time, whatever the calendar says
- The water stays cloudy or foamy after you treat it.
- It has a smell that does not go away.
- Readings will not settle no matter what you add.
This is general guidance. Your hot tub's owner's manual comes first, and so do the instructions on your products.
Sources: Jacuzzi: How often to change hot tub water; Royal Swimming Pools: How often should I change the water in my hot tub?.