Below Skimmer But Above Returns
If the water level drops below the skimmer mouth anywhere down to 18" below the bottom of the skimmer mouth and then stops, you may still have a leak in your skimmer. Quite often you will have an equalizer line in your pool either independently in the wall, or underground connected to the main drain. This allows your skimmer to access water below the mouth of the skimmer, a prevention method to stop your pump from losing prime should the water level fall too low.
A crack in the skimmer itself, or in the pipe connected to the bottom of it would cause the water level to drop to this level and then stop. Skimmers are especially prone to migrating soil conditions, freeze and thaw conditions and contain underground piping that can often be older than the remainder of your pool plumbing. An equalizer from the bottom of the skimmer to the main drains would likely be overlooked during a renovation so it can be a common leak source.
Worth noting also is that a water level in this range could also indicate a broken plumbing pipe underground. The water level in the pool would match the elevation at which the crack exists in the pipe outside the pool
The menu on the right is a chronological step by step process to determine where a swimming pool is leaking. This website is written as a readthrough technical assistance guide for locating leaks. When you believe you have identified where the pool is leaking you need to go to our sister website to see pictures and learn more about the actual swimming pool leak repair process.