: I have purchased a home with heating/cooling radiators in each room. Each unit has a 1/2 copper : drain for the condensate when running the A/C unit. Question: What is the best way to keep these drains open. : The previous owner believed that molds were causing the blockages. Thanks!Hi. Prior to te cooling season Flush the 5/8 copper condensate line out with fresh water. After you do it pour a little bleach to kill any bacteria that may grow. During the season add more water to make sure the drains are still flowing. If possible buy a turkey serenge LOL to help flush it out. Sylvan