pH- A high pH level causes your filter to work harder and the chlorine in your pool to be inefficient. It can also cause cloudy water, scale on the pool walls and floor, discoloration of the pool's surface and eye/skin irritation. pH should be maintained within 7.2-7.8 with a reading of 7.4-7.6 being ideal. To lower the pH of your swimming pool, you will need either dry acid or muriatic acid. The amount needed of either chemical will vary depending on the pool size (gallons) and the pH reading. If your pH reading are not within range, make certain to test for alkalinity as well.
Alkalinity- Alkalinity works with the pH to increase the chlorine's efficiency. Alkalinity also helps prevent the pH from "drifting" or "bouncing". High alkalinity causes cloudy water, scale on the pool walls and floor, discoloration of the pool's surface and eye/skin irritation. To lower alkalinity, you can use either dry acid or muriatic acid. The amount needed of either chemical will vary depending on the pool size (gallons) and the alkalinity reading.
TDS- Total dissolved solids are solids that can't be filtered. These solids are things such as suntan lotion, chlorine, dirt, pollen body waste, stabilizer and algaecides. A high TDS reading will likey mean that the pool remains cloudy no matter how much shock or clarifier is added to the swimming pool. Most swimming pools should be drained and refilled every 3 to 5 years. A normal TDS reading should be 450 ppm or lower. To simplify TDS, imagine an 8 oz. glass of water. If you add a tea spoon of baking soda and stir it, the baking soda will dissolve. If you keep adding baking soda to the same 8 oz. of water, eventually it will not dissolve and the water will appear cloudy. The cloud in the water is a measure of the total dissolved solids. To lower the TDS, the pool will have to be partially drained and refill until the TDS reading is 450 ppm or lower (the lower the better).
Chlorine- In a swimming pool, chlorine should be maintained between 1-3 ppm. When the swimming pool is shocked, that level can spike up to 10 ppm. If the chlorine remains at a high level, bleaching of the pool surfaces can occur. High chlorine will also cause bleaching of swimsuits, eye and skin irritation and bleached hair. To lower chlorine, a chlorine neutralizer can be used, the pool can be partially drained and refilled or you can choose to let the sun burn off the excess chlorine.
Cyanuric acid- Cyanuric acid or CYA should be kept between 30-50 ppm. CYA helps prevents chlorine from being burned off by the sun. CYA levels of 100 ppm or above can cause cloudy water or "chlorine lock". To reduce cyanuric acid levels, you will need to partially drain and refil the swimming pool.