What is the chalk like material for in ground pools?

The chalk like substance you're referring to is likely calcium carbonate, also known as pool scale or limescale. It's a common mineral deposit that forms on surfaces in areas with hard water, which can be a problem for swimming pools. While it's not harmful to swimmers, it can affect the aesthetics of the pool and even damage pool equipment over time.

High levels of calcium and magnesium minerals can cause this scale to build up on pool walls, tiles, and pipes. The main factors contributing to the formation of pool scale are:

- High Calcium Content in Water: If your pool water has high levels of dissolved calcium, it becomes saturated and the minerals start precipitating out of solution, forming scale deposits.

- High pH Levels: A high pH level in pool water makes the water more alkaline and increases the solubility of calcium carbonate. This means that the calcium ions remain dissolved in the water and don't precipitate as scale. However, when pH levels drop (as part of regular pool water maintenance), the calcium carbonate becomes less soluble and forms scale.

To prevent or remove scale buildup in pools, several measures can be taken, including:

1. Water Chemistry Control: Maintaining proper pH levels and calcium hardness levels is essential to prevent scale formation. The water chemistry should be tested regularly and adjustments should be made as needed.

2. Pool Maintenance: Regular pool maintenance, including brushing and cleaning surfaces, can help remove scale buildup.

3. Filtration System Maintenance: Proper filtration and backwashing of the pool filter help to remove scale-forming particles from the water.

4. Water Softeners: If the water source has high levels of calcium, installing a water softener can help to reduce the calcium hardness of the water before it enters the pool.

5. Sequestering Agents: Sequestering agents are chemical products designed to bind with calcium and magnesium ions, preventing them from precipitating out of solution and forming scale.