In an 18,000 gallon pool, 23 fl oz (681 mL) of 10% liquid chlorine raises free chlorine by 1 ppm. The usual evening top-up from 2 to 6 ppm (CYA 40) takes 0.72 gal (2.7 L). With 12.5% chlorine use 18 fl oz per ppm; with 8.25% bleach, 26 fl oz.
| Free chlorine | 10% | 12.5% | 8.25% bleach | 6% bleach |
|---|---|---|---|---|
| Raise 1 ppm | 23 fl oz | 18 fl oz | 26 fl oz | 0.29 gal |
| Raise 2 ppm | 0.36 gal | 0.29 gal | 0.41 gal | 0.58 gal |
| Raise 3 ppm | 0.54 gal | 0.43 gal | 0.61 gal | 0.87 gal |
| Raise 4 ppm | 0.72 gal | 0.58 gal | 0.82 gal | 1.2 gal |
| Raise 5 ppm | 0.9 gal | 0.72 gal | 1 gal | 1.5 gal |
| Shock 2 → 16 ppm | 2.5 gal | 2 gal | 2.9 gal | 4.1 gal |
Add
0.72gal
of Liquid chlorine 10%
92 fl oz2.7 L
Raises free chlorine from 2 ppm to 6 ppm in 18,000 gal. Best added at dusk.
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.
With CYA at 40 ppm: minimum free chlorine 3 ppm, target 6 ppm, shock level 16 ppm. FC/CYA chart
Save this test and get reminded when it is time to retest.
Pool Calc for iPhoneComing soon to the App StoreLiquid chlorine adds almost nothing but chlorine. As it is used up it leaves a little salt behind (about 1.6 ppm per ppm of chlorine), which is harmless. It loses strength in storage, faster in a hot garage, so buy it fresh and keep it shaded.
Your target depends on your stabilizer (CYA). At CYA 40 the minimum is 3 ppm and the daily target about 6 ppm. At CYA 60 those become 4.5 and 7.5 ppm. Shocking at CYA 40 means holding 16 ppm, which takes 2.5 gal (9.5 L) from 2 ppm in this pool.
Never pour chlorine and acid together or in the same spot. Add one, run the pump for 30 minutes, then add the other.
That is about the size of a 27 ft round × 54 in above-ground pool (about 17,130 gal), or a 16 × 32 ft in-ground pool averaging 5 ft deep (about 19,150 gal), or a 15 × 30 ft in-ground pool averaging 5 ft deep (about 16,830 gal). 18,000 gallons is a typical backyard pool. Measure the volume once rather than trusting the builder’s brochure: an error of 20% in gallons makes every dose 20% off. The pool volume calculator takes a minute.
About 23 fl oz of 10% liquid chlorine per 1 ppm of free chlorine. To go from 2 to 6 ppm, add 0.72 gal.
At CYA 40 the shock level is 16 ppm. From 2 ppm that is 2.5 gal of 10% liquid chlorine. Higher CYA needs more: the shock level is 40% of CYA.
Yes, if it is plain unscented bleach. It is weaker, so use more: 26 fl oz of 8.25% bleach per ppm in 18,000 gallons.