Spa Calc

How much bleach for your hot tub, by size

Plain unscented household bleach (6% to 8.25%) or pool liquid chlorine (10% to 12.5%). Pick your tub size for a full table, or use the calculator for any volume.

Any other size

gal

Not sure? Find your tub’s volume.

%
ppm

Fresh water: 0. Dichlor raises it about 0.9 ppm per 1 ppm of chlorine.

ppm
ppm

Set from your CYA until you change it. Hot tubs: 3 to 5 ppm (CDC minimum 3; many labels say not to soak above 5).

Add

0.29oz

of Dichlor granules 56%

8.1 gabout 1⅞ tsp by volume

Raises free chlorine from 1 ppm to 4 ppm in 400 gal.

  • Side effects: CYA +2.7 ppm, TA −1.1 ppm.
  • Also raises cyanuric acid (stabilizer). It only comes down by replacing water.
  • Run the jets with the lid open and wait at least 15 minutes (20 after pH decreaser) before anyone gets in.
  • Pour it slowly in front of a return jet with the pump running.

Check the product label. Strengths vary by brand, so enter the % printed on yours. Add one chemical at a time, into the water, and never mix chemicals.

Use dichlor for the first week or two until stabilizer reaches about 30 ppm.

Save this test and get a reminder before your next soak.

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