How often should I change hot tub water?
Cal Spas' owner's manual says to drain a spa every four to six months and refill it with fresh tap water. A tub used daily by several people belongs at the short end, and your own manufacturer's interval takes precedence. Between changes, test weekly and deep-clean the filter at least monthly, or every two weeks with heavy use.
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By Kasra Taheri, Founder, LoclisPublished
Researched and drafted with AI, then checked claim by claim against the sources listed below before it was published. Prices and rules change; the dates beside each source say when it was last checked.
Step by step
Read when to stop and call a pro, further down this page, before you start.
Step 1: Find your maker's interval
Look in your owner's manual for how often to drain; Cal Spas says every four to six months.[1]
Step 2: Write down the refill date
Note the date of each refill on the cover or in a phone reminder so the next change is not a guess.
Step 3: Adjust for how much you use it
Shorten the interval if several people use the tub often or for long soaks, because bather load drives how fast the water wears out.[1]
Step 4: Test every week
Check sanitizer, pH and alkalinity weekly and correct them; the manual says to check pH on a regular weekly basis.[1]
Step 5: Clean the filter between changes
Deep-clean the filter at least monthly, or every two weeks with heavy use.[1]
Step 6: Drain early when the water fights back
If the water will not hold its balance, stays cloudy or keeps foaming after the filter is clean, change it now instead of waiting for the date.
Step 7: Drain, clean and refill
Follow the drain-and-clean method for your tub and refill with regular tap water.[1]
Plan on draining and refilling a hot tub roughly every four to six months, sooner if it gets heavy use and later only if your maker says so. Cal Spas' owner's manual puts it this way: "Your spa should be drained every four to six months for cleaning and maintenance and refilled with fresh tap water."[1] Other manufacturers publish their own numbers, so your manual outranks any rule of thumb.
What sets your interval
The main factor is how much the tub is used. Cal Spas' manual explains that the higher the bather load, "the more chemicals need the be added and a longer filtration time will be needed."[1] Its baseline recommendations assume an average load, which it describes as 3 to 4 people, 15 minutes of usage, three times a week at 100 degrees.[1] A tub that sees more than that wears out its water faster.
Other things shorten the wait: lotions and sunscreen on the bathers, a filter that has gone too long without cleaning, and water that keeps going out of balance no matter what you add. A weekly test is how you notice.
A tub used lightly, with a clean filter and steady chemistry, can reasonably stay at the long end of the range. Do not stretch past what your manual says.
What to do between changes
Changing the water is only half the routine. Keep the water in good shape in between:
- Test sanitizer, pH and alkalinity weekly and correct them. The manual says to check the pH on a regular weekly basis.[1]
- Deep-clean the filter. Cal Spas recommends "cleaning your filter at least once a month or every two weeks depending on spa usage."[1]
- Keep the cover on when the tub is not in use, and rinse off before getting in.
Signs to change it early
- The water stays cloudy after the filter is clean and the chemistry is corrected.
- It will not hold its balance, so you are adding chemicals every day.
- It foams repeatedly. See why hot tub water gets foamy.
- It smells even after you shock it.
If one of these is happening, do not wait for the calendar.
Refilling
Fill with "regular tap water about six inches from the top."[1] The manual is blunt about one thing: "Never fill with soft water."[1] The full sequence, including the filter soak and shell cleaning, is in how to drain and clean a hot tub.
Where the water goes
Old hot tub water carries sanitizer. Prince William County's ordinance allows only "de-chlorinated, pH neutral, chemical-free, clean water" to be slowly discharged to the storm drain, and the county suggests that you "allow untreated water to sit for approximately 10 days to allow the chlorine or bromine to dissipate."[2] Stafford County lists dechlorinated swimming pool discharges among the allowable ones.[3] These are county rules, not a statewide one, so ask your own locality before you drain toward the street.
Stop and call a pro if
- The GFCI trips or the tub will not power up after a refill. Do not keep resetting it; have a qualified technician look at the wiring.
- The tub leaks or loses water between fills.
- It will not drain, or water keeps coming back to the drain valve after it is closed.
- Pumps are noisy, dry or sucking air after you refill.
Getting help in Virginia
If a drain-and-refill schedule is more than you want to take on, read whether a hot tub maintenance service is worth it and what hot tub service costs in Virginia. Browse pool and spa answers or pool and spa services on Loclis.
When you are ready, describe your hot tub once and local pros quote it.
Common questions
- Is every three months too often to change hot tub water?
- Not for a tub that is used heavily. Cal Spas' manual gives a range, "every four to six months,"[^calspas] and says a higher bather load needs more chemicals and longer filtration.[^calspas] A tub used daily by a household sits at the short end, or just under it.
- Can I just top up the water instead of changing it?
- Topping up replaces what splashes out, but it does not remove what has built up in the water. Draining on the maker's schedule is how that gets reset.
- Can I fill the tub with softened water?
- No. The Cal Spas manual says "Never fill with soft water."[^calspas]
- Where can the old water go?
- Prince William County says only "de-chlorinated, pH neutral, chemical-free, clean water" may be slowly discharged to the storm drain, and suggests letting untreated water sit for about 10 days for the chlorine or bromine to fade.[^pwc] Stafford County lists dechlorinated swimming pool discharges among the allowable ones.[^stafford] Rules vary by locality, so ask yours.
Sources
- [1] Patio and Patio Plus Owner's Manual 2025, Cal Spas. Checked October 27, 2026.
- [2] Stormwater Pollution Reduction, Prince William County, Department of Environmental Services. Checked October 27, 2026.
- [3] Illicit Discharge, Detection, & Elimination Program, Stafford County, Virginia. Checked October 27, 2026.
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