How often should you change hot tub water?

Short answer

Every 3 to 4 months for most owners, the interval Hot Spring and Caldera print; Jacuzzi says every 3 months and Master Spas at least every 180 days. CDC's formula puts a 345-gallon tub used by two people a day at 58 days.

Updated October 2026By the HotTubFinder research desk

A year of hot tub care: test the water each soak and three times a week, clean the filter monthly, drain and refill every 3 to 4 months, a new filter once a year — Where a water change fits in the care routine.

How often each maker says to change the water

6 makers

How often six makers say to change hot tub water
Maker	Change the water
Bullfrog X Series	Every 1 to 4 months
Caldera	Every 3 to 4 months
Hot Spring	Every 3 to 4 months (up to 12 with its salt system)
Jacuzzi	Every 3 months
Master Spas	At least every 180 days
Sundance	Every 3 to 6 months

From each maker's current owner's manual, makers A to Z. Checked October 2026.

How do you work out when to change hot tub water?

CDC's hot tub toolkit gives a formula: divide the tub's gallons by 3, then by the average number of people using it each day. The answer is days between water changes. It was written for public tubs, but the logic holds at home: every bather adds sweat, oils and soap the chemicals can't fully remove, so more bathers per gallon means shorter water life.

At one soak a day, the formula lands where the makers do: a 345-gallon tub comes out at 115 days, close to four months. At two soaks a day it is 58 days, and at four it is 29.

Days between water changes by tub size, CDC's formula applied to our spec sheets

2 seats14 spec sheets	160 gal	53 days	27 days	13 days
3 seats38 spec sheets	219 gal	73 days	37 days	18 days
4 seats26 spec sheets	240 gal	80 days	40 days	20 days
5 seats60 spec sheets	306 gal	102 days	51 days	26 days
6 seats136 spec sheets	392 gal	131 days	65 days	33 days
7 seats64 spec sheets	395 gal	132 days	66 days	33 days
8 seats11 spec sheets	490 gal	163 days	82 days	41 days
9 seats8 spec sheets	518 gal	173 days	86 days	43 days

Median gallons by seat count across 363 published spec sheets (seat counts with 5 or more). Days = gallons ÷ 3 ÷ bathers a day, rounded. Find your own tub's gallons in our gallons and filter size table.

How do you know hot tub water needs changing?

The water stops behaving even though the tests look right. Jacuzzi and Sundance both describe it the same way: you can't control sudsing, or the water has lost its usual feel and sparkle with every reading in range. Bullfrog adds chemistry that has become hard to manage. Hot Spring's reason is soap: it concentrates until the water leaves skin feeling unclean, and nothing but fresh water fixes it.

Why does hot tub water wear out?

Two things pile up. Soap and oils come in with every bather and no chemical removes them. And when water evaporates, only pure water leaves; salts, minerals, metals and used-up chemicals stay, and each top-up adds more. That is also why an unused tub still needs fresh water now and then.

Do salt water hot tubs need fewer water changes?

Some last longer. Hot Spring says water kept with its salt system can last up to twelve months with proper care, against three to four months otherwise. See salt water hot tubs. When it is time, follow how to drain and refill a hot tub.

The details

The full tables, the figures behind each sentence and where they come from.

The figures at a glance

Makers' range

1 to 6 months

six owner's manuals

345 gal, 2 bathers a day

58 days

CDC formula

Median tub

345 gal

363 spec sheets

Common questions

How often should you change hot tub water?

Every 3 to 4 months for most owners. The six manuals we read range from every 1 to 4 months (Bullfrog) to at least every 180 days (Master Spas).

How do I calculate when to change my hot tub water?

CDC's formula: divide the tub's gallons by 3, then by the average number of bathers a day. A 345-gallon tub used by two people a day comes to about 58 days.