We stock every part for the Armstrong EHU-500 Series Steam humidifier ever made. Our technical support team can assist you should you have any questions about your Armstrong EHU-500 Series steam humidifier. Order from the source of parts just like the contractors do. You will find on-line owners manuals as well as exploded views of your model on its associated humidifier parts page. Remember to replace or clean your steam tank at least once per year for optimal operation. Most Models will bring up a warning indicator when the steam tank fails. Unfortunately you must view the unit periodically to know when it is time. We recommend you clean or replace the steam tank at least once per year for residential applications and more often for commercial and industrial humidification needs.