Auto-fill is a "plumbed" feature that uses a water connection and a solenoid to automatically fill each pan of a Modular/Ganged Heated Well to the desired level. This ensures that all pans are always full of water - even when evaporation can become a big issue. During the day, as the steam table evaporates water out of each pan location, the auto-fill feature will sense the lack of water and open the solenoid, allowing water to re-enter each pan until the desired water level is reached. With 2-, 3-, 4- and 5-pan wells, this feature will only work if the unit has a manifold drain.