How often to change hot tub water

The rule of thumb is gallons ÷ 3 ÷ average daily soakers. Jacuzzi's guide uses the same formula and puts the typical interval at every 3–4 months.

Calculator: gallons, soaks per day

Count soakers per day as an average over a week: two people soaking every evening is 2; four people on weekends only is about 1.1. Don't know your volume? See how many gallons a hot tub holds.

Signs to drain early

Hot water, a small volume, and many soakers per gallon make hot tub water "fill up" with dissolved material much faster than pool water. Drain before the calculator date if you see:

• Cloudy or foamy water that returns after shocking. See why hot tub water foams.
• A musty or strong chemical smell, or combined chlorine (total minus free) that will not drop.
• High total dissolved solids (TDS). Jacuzzi says to drain when TDS exceeds 1,500 ppm; industry guidance cited in our methodology uses 1,500 ppm above your fill water.
• Stabilizer build-up from dichlor. Each 1 ppm of chlorine from dichlor adds 0.9 ppm of stabilizer (CYA). Two ppm a day for 30 days adds about 54 ppm, which makes chlorine work more slowly. Hot tubs are meant to run without CYA (CDC).
• Chemistry that won't balance: pH that swings, or doses that no longer do what they used to.

How to drain and refill

1. Turn off power to the hot tub at the breaker, so the heater and pumps cannot run dry.
2. Take out the filter cartridges.
3. Drain through the tub's drain valve with a garden hose, or use a submersible pump for speed. Check your local rules on where treated water can go. Letting chlorine drop to zero first protects lawns and storm drains.
4. Wipe the empty shell with a mild, non-foaming cleaner and rinse well so no cleaner ends up in the new water.
5. Clean the filter cartridges, or replace them if they are worn or discolored.
6. Reinstall the filters and refill with a garden hose. If your manual says to fill through the filter well, do so.
7. Restore power and let the tub circulate and heat. Test the water before the first soak.

Jacuzzi's guide follows the same outline: power off at the breaker, remove the filters, drain, clean the interior, refill, then test and balance.

Start-up after refill

Fresh water has no sanitizer, and its pH and alkalinity come straight from your tap. In order:

1. Alkalinity to 80–120 ppm first; it steadies pH.
2. pH to 7.4–7.6.
3. Calcium hardness to 150–250 ppm if your water is soft.
4. Sanitizer: free chlorine 3–4 ppm or bromine 4–6 ppm (CDC minimums: 3 ppm chlorine, 4 ppm bromine). If your chlorine label sets a different soaking limit, use that number.
5. Shock after the first heavy use.

The beginner's guide to hot tub chemicals explains each product. Our hot tub maintenance schedule puts water changes, filter rinses, and tests on one calendar. Keep water at or below 104 °F.

FAQ

How often should I change my hot tub water?

Estimate with gallons ÷ 3 ÷ average daily soakers: about 67 days for a 400-gallon tub used by two people a day, 35 days for a 210-gallon inflatable used by two. Jacuzzi suggests every 3–4 months on average. Drain sooner if water stays cloudy, foamy, or smelly after shocking.

How do you get water out of a hot tub?

Turn off power at the breaker, then drain through the built-in drain valve with a garden hose attached, or lower a submersible pump into the tub for a faster drain. Remove the filters first and clean them before you refill.

Sources

• Jacuzzi, How often to change hot tub water (formula, 3–4 months, TDS, drain steps): jacuzzi.com
• CDC, Home pool and hot tub water treatment and testing (hot tub chlorine and bromine minimums): cdc.gov
• Dichlor stabilizer build-up (0.9 ppm CYA per 1 ppm FC, PHTA), TDS guidance, and hot tub targets: methodology