If your distiller doesn’t seem to be producing the same amount of water as what you’ve added in, there might be a number of factors to blame. First of all, check that your distiller is fully plugged in both at the unit and at the wall. It sounds obvious, but if an adequate power supply can’t run into the machine, the fan won’t work properly, and some of the steam might end up leaving the distiller and evaporating into the air.
You might also experience a smaller distilled water production if your gasket is damaged or worn. This is more common in older distillation units, and is a sign that you’ll need to buy a replacement part.