The purifier tank is advertised as holding a gallon of water, but in reality, it only filters about 3/4 of a gallon. This discrepancy is a bit frustrating, as the marketing led me to expect a full gallon of filtered water. That said, the purifier itself functions adequately and does its job, though the capacity shortfall is a huge letdown. If you’re okay with slightly less filtered water per use, it works fine, but clearer advertising would have been appreciated.