Our technical support team can assist you should you have any questions about your Herrmidifier RDU-D Steam humidifier. Remember to replace your Herrmidifier Steam tank at least once per year for optimal operation. Most Herrmidifier Steam humidifiers will bring up a warning sign when the steam tank fails. Unfortunately you must view the unit periodically to know when it is time. We recommend you replace the steam tank at least once per year for residential applications and more often for commercial and industrial humidification needs.