Pool chemicals are added in relation to the number of gallons of water. Most chemicals instruct users to add a specific amount for every 5,500 to 7,000 gallons of water. For example, if you have a round 24-foot aboveground pool that is 4 feet deep, you have approximately 12,000 gallons of water. A 12-by-24-foot oval aboveground pool that's 4 feet deep has about 6,000 gallons. The chemical should be added based on the gallons of water in your pool.
Turn on the pool filter and keep it running to eliminate dirt and debris in the water. Dip a test strip a foot under the surface and note the readings, which should include chlorine, pH and alkalinity. Decide what you need to add to the water. If this is the first time adding chemicals, you will most likely receive a low chlorine reading. Alkalinity and pH levels should not have to be adjusted as much, but they can fluctuate after adding chlorine.
Add shock to the water. One gallon of shock will treat 5,500 to 7,000 gallons, depending on the label. Add shock to the water around the perimeter of the pool. For a 24-foot round pool you will need at least 2 gallons, which can treat 11,000 to 14,000 gallons. After adding the shock, let the filter run for at least 12 hours before taking another reading with test strips.
Test the water again with a test strip and note chlorine, pH and alkalinity levels. It will be time to add chlorine, the amount of which will depend on the gallons of water and what the test strip indicates. The chlorine will have a chart on the back and a scooper inside the bucket to indicate how many scoops to add per 5,500 gallons of water. For a 5,500-gallon pool, one scoop of chlorine every few days dispersed on the surface of the water is adequate for basic maintenance.
Adjust the pH and alkalinity levels with Up or Down products, available from pool supply stores. If you chlorinate and clean your pool regularly, pH and alkalinity levels tend to stay in normal ranges as indicated on test strips.
Determine which chemicals to add if levels are not in normal ranges according to the test strip. For example, if the pH is low, add a pH up chemical to the water. The bottle will indicate amounts to add for every 5,500 to 7,000 gallons of water. If you have more than 10,000 gallons, you'll likely need to double the chemicals added.