What is wrong with your pool if you get a white powerdy build up on fingers when rub the walls of fiberglass and after using for day find water becomes milky?

The white powdery buildup on your fingers when you rub the walls of your fiberglass pool and the milky water after a day of use are indicators of a calcium hardness issue. Here's what's happening and how to address it:

1. Calcium Hardness: Calcium hardness refers to the amount of dissolved calcium in your pool water. When calcium hardness is too high, it can cause scaling, cloudiness, and other problems.

2. Scale Buildup: The white powdery buildup on your pool walls is likely calcium scale. This scale forms when calcium carbonate, which is a compound made up of calcium and bicarbonate ions, precipitates out of the water and forms a solid deposit.

3. Milky Water: The milky appearance of your water is caused by tiny suspended calcium carbonate particles. These particles scatter light, giving the water a cloudy look.

To resolve these issues, you'll need to lower the calcium hardness in your pool water. Here are the steps to take:

1. Test Your Water: Use a pool water test kit to accurately measure the calcium hardness level. The ideal range for calcium hardness is typically between 200 and 400 ppm (parts per million).

2. Drain the Pool: Drain a small amount of water from the pool to reduce the overall volume and calcium content. The amount you drain will depend on your pool size and the current calcium hardness level.

3. Add a Sequestering Agent: Sequestering agents, also known as chelating agents, bind with metal ions such as calcium and prevent them from forming scale. Add the sequestering agent according to the manufacturer's instructions.

4. Adjust the pH: Ensure that the pool water pH level is within the recommended range of 7.2 to 7.8. This will help prevent corrosion and scaling.

5. Monitor the Calcium Hardness: Regularly test your pool water to monitor the calcium hardness level. If it starts to rise again, you may need to drain some water and add more sequestering agent.

By lowering the calcium hardness and using a sequestering agent, you can prevent scale buildup and keep your pool water clear and sparkling. If the problem persists or you have difficulty managing the calcium hardness level, it's a good idea to consult with a pool care professional for further assistance.