The highest safe water level is the highest point the water can reach inside the sump pump basin without causing any problems. If the water level goes higher than the "highest safe water level," it can cause damage to your house.
The indicators of the highest safe water level in a sump pump basin can vary depending on the specific design and features of the basin. Here are some common indicators that can help determine if the water level is getting too high:
Float Switch: Sump pump basins have a float switch, which is a part of the pump system that floats on top of the water. The highest safe water level is the water level at which point the float switch triggers the sump pump to start working and remove the excess water.
Backup Pump: Some sump pump basins have a backup pump that runs in emergency situations when the main pump fails to trigger. The backup pump's float will trigger if the water in the basin reaches that level. In this case, the highest safe water level is above the backup pump float.
Water residue on the sump pump basin: If a sump pump has no mechanisms indicating the highest safe water level, an additional indicator can be water residue on the wall of the sump pump basin, indicating the typical highest safe water level.