The water level in my H5i does not seem to drop very far even though I used it for a full night. Is this normal?

Yes. The water level left after use doesn’t give the best indication of unit function. As the H5i provides constant moisture output, it only uses the amount of water needed to provide the required level of moisture. If set at the same Climate Control temperature throughout the year, the H5i will use significantly less water during summer than it will during the winter.