Draining a concrete pool is generally not recommended because it can cause structural damage to the pool. Concrete pools are built on a foundation of soil and rock, and when the pool is full, the water helps to hold the soil in place and maintain the structural integrity of the pool. When the pool is drained, the soil can shift, which can cause cracks and other damage to the pool.
Additionally, when concrete pools are drained, the walls and floor of the pool can shrink and crack, which can lead to leaks and other problems. Also, the water pressure that is exerted on the pool's structure when it is full is necessary to keep the pool walls and floor stable and in place.
Furthermore, when a pool is drained, the pool shell can become extremely dry and brittle, which can make it more vulnerable to cracking and breaking.
It's also important to note that if you drained a concrete pool, it would take a lot of water to fill it up again and the process of refilling would cause the soil to shift and the pool to crack.
If you need to do repairs on your concrete pool, it's best to consult a professional pool contractor who will be able to properly assess the situation and give you a personalized solution that will not involve draining the pool.