How much shock for a 5,000 gallon pool

To shock a 5,000 gallon pool with CYA 40, raise free chlorine from 2 to 16 ppm with 14 oz (408 g) of 65% cal-hypo shock (about 0.9 one-pound bags). Each 1 lb bag raises free chlorine by 16 ppm in 5,000 gallons. The shock level is 40% of your CYA, so test CYA first.

Shock doses for 5,000 gallons by CYA level

5,000 US gallons (18,927 L).
From FC 2 to	65% cal-hypo	73% cal-hypo	Calcium added
CYA 30 → 12 ppm	10 oz	9.1 oz	+7 ppm
CYA 40 → 16 ppm	14 oz	13 oz	+10 ppm
CYA 50 → 20 ppm	1.2 lb	1 lb	+13 ppm
CYA 60 → 24 ppm	1.4 lb	1.3 lb	+16 ppm
CYA 80 → 32 ppm	1.9 lb	1.7 lb	+21 ppm

Run it with your numbers

Add

14oz

of Cal-hypo shock 65%

408 g

Raises free chlorine from 2 ppm to the shock level of 16 ppm (40% of CYA 40) in 5,000 gal.

Side effects: CH +9.9 ppm.
Pour it slowly in front of a return jet with the pump running.
Dissolve it in a bucket of pool water first, then pour it in front of a return jet.
Hold free chlorine at 16 ppm: retest and top up at least morning, midday and evening.
You are done when combined chlorine is 0.5 ppm or less, the overnight chlorine loss is 1 ppm or less, and the water is clear.
No swimming during the SLAM. Swim when free chlorine is back within your normal range and at or below the re-entry level on your chlorine label (many labels say 4 ppm). Never swim during a SLAM or with free chlorine above 10 ppm. Your product label always comes first.
Repeated shocks with this product build up its side effect. Liquid chlorine adds nothing but chlorine and a little salt.

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.

Save this test and get reminded when it is time to retest.

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About shock

Cal-hypo adds calcium: about 0.7 ppm of calcium hardness for every 1 ppm of chlorine. One shock at CYA 40 adds about 10 ppm, which matters in vinyl pools and where the fill water is already hard. If you shock often, 0.7 gal of 10% liquid chlorine does the same job with no calcium.

Dissolve cal-hypo in a bucket of pool water first and pour it in front of a return. Never mix it with any other chlorine product, especially trichlor tablets: the combination can ignite.

A shock (SLAM) is not one dose. Hold free chlorine at the shock level, testing and topping up several times a day, until combined chlorine is 0.5 ppm or less, the overnight loss is 1 ppm or less, and the water is clear.

Dosing a 5,000 gallon pool

That is about the size of a 15 ft round × 52 in above-ground pool (about 5,070 gal), or a 16 ft round × 48 in above-ground pool (about 5,260 gal). At 5,000 gallons, most doses are measured in fluid ounces or ounces rather than gallons or pounds. Above-ground pools of this size usually have vinyl liners, so keep calcium hardness modest and add everything in front of a return jet, away from the liner wall.

Questions

How many bags of shock for a 5,000 gallon pool?

At CYA 40, about 14 oz of 65% cal-hypo, from 2 ppm to the 16 ppm shock level. Each 1 lb bag adds 16 ppm.

Can I swim after shocking?

Swim when free chlorine is back within your normal range and at or below the re-entry level on your chlorine label (many labels say 4 ppm). Never swim during a SLAM or with free chlorine above 10 ppm. Your product label always comes first.

Is liquid chlorine better than shock?

Both are chlorine. Liquid chlorine adds no calcium or stabilizer, so it suits repeated shocking. Cal-hypo is easier to store but raises calcium hardness.