Your pools main drain line was probably not winterized properly or the valve that locked air in the line was bad leaky or the plug used to lock air in the line popped out.
Swimming pool bottom drain leak.
This could easily account for a leak in the main drain of a pool.
The equalizer line in the pool is a non pressurized pipe that connects from the main drain to the underside of the skimmer therefore often left even in major renovations.
Use a leak detection service to pinpoint the leak.
Remove the cover from the main drain with a screwdriver.
Use a submersible pump to drain the pool completely of all water.
Turn off all circuits and power to the pool equipment.
If this happened then it is possible for your entire pool to drain out through the bottom of the main drain.
Leaks in equalizer pipes are one of the most likely suspects with older swimming pools.
Use a small cup to remove any water in the main drain.
Call your trusted leak detection company right away if you suspect you have a leak.
These services will save hours of time and a lot of money as they have the experience and tools to locate these leaks.
It is also fairly common for hydrostatic relief valves to get stuck open from debris obstructing the valve from closing.
You might need to use a small bucket to remove any leftover water the pump was unable to drain.
An underground pool pipe leak can be tricky to pinpoint depending on the location and the slope of the ground surrounding your pool or spa tub.
The most common reason for leak.
Chart the main drain.