Above Ground Pool Chemicals

A few basics cover cleaning, testing and balancing the water, whatever pool you have:

• Liquid chlorine
• Strips for testing the water
• pH down and pH up (soda ash)
• Baking soda, which lifts alkalinity
• Stabilizer (cyanuric acid). Test before adding any, and aim for 30 to 50 ppm.

Once stabilizer is in the water it stays, so add small amounts and retest before adding more.

How many gallons your pool holds drives every dose. Check your pool's water capacity before dosing, or work it out from its surface area and average water depth.

For a round or oval pool, take the surface area in square feet, multiply by the average depth in feet and then by 5.9. A rectangular pool uses 7.48 instead of 5.9. When the floor slopes, find the average depth by adding the shallow and deep depths together, then dividing by 2.

Every dose listed here uses US gallons, and a single US gallon holds 3.785 liters.

In a small pool, lifting free chlorine by 1 ppm takes just a few ounces.

Each amount here fits a 5,000-gallon pool. For a 10,000-gallon pool, double each amount.

• To lift free chlorine by 1 ppm: 5 fl oz of liquid chlorine at 12.5%
• To lift free chlorine by 1 ppm: 1 oz of cal-hypo at 65% (30 g)
• To shock, raising free chlorine by 10 ppm: half of 102 fl oz (3.03 L) of 12.5% liquid chlorine, a bit under half a gallon
• To lower pH from 7.8 to 7.5: about 4.5 fl oz of muriatic acid at 31.45%, half of 9 fl oz (270 mL)
• To raise pH from 7.2 to 7.5: half of 1 lb 1 oz (495 g) of soda ash
• To lift alkalinity 10 ppm: half of 1 lb 6 oz (635 g) of baking soda
• To lower alkalinity by 10 ppm: half of 26 fl oz (755 mL) of muriatic acid at 31.45%, so 13 fl oz
• To lift stabilizer by 10 ppm: half of 13 oz (380 g) of cyanuric acid
• To lift calcium hardness by 10 ppm: half of 1 lb 3 oz (545 g) of calcium chloride at 77%

That acid dose for dropping pH works if alkalinity sits in its normal range. A shock is a far bigger chlorine dose than routine use.

Order matters, because a small pool responds fast.

1. 1. Have the pump running before you add anything, so the chemical spreads through the water right away.
2. 2. Add the chemical in front of a return jet, the spot where water flows back in, so it mixes rather than pooling in one place.
3. 3. Never mix products. Add them one at a time. In particular, keep acid away from chlorine, because they react badly together.
4. 4. If you dilute acid, the acid goes into the water. Never the other way around.
5. 5. Thirty minutes after adding acid or soda ash, test pH again, since a small pool can overshoot.

A normal amount of liquid chlorine usually means you can swim again in around 30 minutes. After a shock, hold off until testing shows free chlorine back in its normal range for your stabilizer, and never swim above 10 ppm.

Stabilizer does not break down or filter out, so the level only goes down when you replace water. When it gets too high, the only answer is draining some water and refilling. Getting from 100 ppm to 50 ppm calls for swapping out around half the water.

All the water should move through the filter once per day. That's one turnover, and it usually runs about 8 hours. Give it an extra 1 to 2 hours during hot spells or after lots of swimming. A standard single-speed pump draws about 13.8 kWh over 8 hours of running.

Evaporation takes roughly a quarter inch of water a day, and heat plus wind push that higher, per Latham Pool. To check for a leak, fill a bucket with water, then compare how far the pool and the bucket drop over 24 hours. If the pool falls more than 1/8 inch beyond the bucket's own drop, water is likely escaping somewhere.