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Get a quality pool test kit at your local pool supply store or online. The kit may use test strips or a drop test. Check that the free chlorine levels are 1-3 parts per million (ppm). Make sure the pH levels are at 7.2-7.8. This will ensure the pool stays clean and functions well.  If you need to lower the pH levels in the pool, you can add muriatic acid to the water. To raise the pH levels, add sodium bicarbonate. Consult your owner's manual or speak to a professional salt pool cleaner if you need guidance. The stabilizer levels help to prevent the chlorine in your pool from being lost due to UV rays from the sun. Use a test kit to check the stabilizer levels. If you have an outdoor pool, make sure the stabilizer levels are at 70-80 ppm. If you have an indoor pool, you should have stabilizer levels at 0-30 ppm.  You can lower the stabilizer levels by draining the pool and adding fresh water to dilute the pool water. You can raise the stabilizer levels by adding cyanuric acid to the pool water, based on the manufacturer's instructions. The alkalinity level helps to keep the pH level stable. It should be between 80-120 ppm. You can bump up the alkalinity level by adding baking soda to the water and reduce it by adding muriatic acid.  The calcium in the water helps to prevent the water from becoming corrosive and cloudy. It should be at 200-400 ppm. You can add calcium to the pool to bump up the calcium level and reduce the amount you add to bring the calcium level down. The salt level should be in the range specified by the manufacturer of the pool. This is usually around 2700-4500 ppm. You can add more salt to the water to bump up the salt level to where it should be. Always make sure the cell in your pool is working so the salt can circulate properly. Make sure metals like copper, iron, and manganese are not present in the water by using a test kit. Check for metals when you add fresh water or at the start of the pool season. These metals can lead to corrosion and other issues in the pool if they are present.

Summary:
Use a test kit to check the free chlorine and pH levels weekly. Check the stabilizer levels weekly. Check the alkalinity, calcium, and salt levels once a month with a test kit. Check that there are no metals in the water.