Installed new Aprilaire power fan humidifier. Added new 1/4 inch hot water line and 120 volt receptacle to power humidifier. Added new custom overflow safety pan with float switch under humidifier in case of a leak because system is located on second floor. Ran new 3/4 inch pvc drain line that is also tied in with a drain from the new overflow safety pan. Noticed that ST 5 expansion tank on water heater had failed. Replaced with new ST 5 expansion tank and properly braced tank up incase of failure in the future. Tested and cycled humidifier and it is operating properly at this time.