Before draining a swimming pool, you must obtain a pool drain permit. Pool water may not be drained anywhere except to the sanitary sewer system. Either the pool owner or the pool contractor will need to contact the Pretreatment Program at 408-846-0451 to start the process. The program is managed regionally by the City of Gilroy.
A pool remodel that requires a permit from the Building Department would also require a pool drain permit. After approval, you will need to coordinate with an inspector to meet at the property. The inspector will determine the location to drain the pool water and then the pool can be drained and the work can be completed.
Note that if you only need to lower the height of the pool water, you can pump the water to a sanitary sewer clean out, which is often adjacent to the kitchen, for example it is to serve the kitchen sink, without obtaining a permit.