Understanding Swimming Pool Chemistry

Water Capacity and Testing

• Water capacity is the most important factor in pool chemistry, even though no chemicals are involved. The number of gallons in your pool determines how much of which chemicals you will routinely add to your water. All chemicals for your pool are measured in amounts that depend on the pool's capacity. If you think your pool holds 10,000 gallons but its true capacity is just 5,000, you'll be unable to properly balance the water chemistry.

Alkalinity and pH

• The total alkalinity and the "pH level" are two key aspects of water chemistry. Total alkalinity measures the amount of alkaline present in the water, while pH refers to the relative degree of acidity or alkalinity in the water. Total alkalinity stabilizes the pH in your pool. You should balance the alkalinity with chemicals before balancing the water's pH, since pH often returns to its normal range once you've balanced the alkalinity. Use a testing kit or testing strips to determine whether the total alkalinity and pH are high or low. Pool chemicals to raise or lower alkalinity and pH are available at pool retailers.

Chlorine

• Chlorine is the most popular sanitizer. There are several alternatives to chlorine, such as bromine and salt water systems. All of these are considered sanitizers and are the most important aspect of pool maintenance, because they kill germs and bacteria. When the water is clean the pH and alkalinity are less likely to get out of their normal range. The testing kit will tell you when it's time to add chlorine to the water. Again, the amount of chlorine added to the pool is in accordance with your pool water capacity.

Stabilizer

• A chlorine stabilizer can save you money on chlorine, especially if you live in a hot climate. Chlorine dissipates in the water much faster as temperatures rise. Chlorine stabilizer will preserve the chlorine in your pool and make it last longer, thus saving you money as well as time spent on maintenance. Some chlorine products, such as chlorine tablets, are made with chlorine stabilizer included. The same testing kit or strips used to measure chlorine, pH and alkalinity can determine stabilizer levels, too. Stabilizer is optional, though, since a pool can still be kept clean without it.

Calcium Hardness

• Calcium hardness also must be measured as part of pool maintenance. Most testing strips won't be able to test calcium hardness. A separate testing kit or testing strips are needed. High calcium-hardness levels in your pool mean the water contains excess calcium and magnesium, which can form crystallized clumps in your pool. A low calcium-hardness level can lead to premature corrosion of plaster pool walls and accessories, such as your pool ladder. Chemicals are available that can help stabilize calcium-hardness levels.