Scale is the natural enemy of electric water heaters. In addition to tap water scale, water inside the water heater can also produce scale when heated. Scale often adheres to the heating pipes and the inner tank of the water heater, which greatly reduces thermal efficiency. If you find that the heating time is long or there is a "horn" sound during heating, it indicates that the electric water heater needs to be cleaned. Therefore, it is recommended that you regularly clean scale.