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Expansion Tank Errosion on closed loop glychol system low pressure

expansion tank water worker m 30 erroaded with blistering and pin holes leaking toxic antifreeze on outside surface . also some corrosion at solder joints on copper feed lines. the first tank lasted over 15 years,the 2nd lasted 2 years and the current tank started eroading at 6 months. are these tanks lined? do I need a better expansion tank or could there be another problem?


  • Docfletcher
    Docfletcher Member Posts: 481
    Photos please. Hydronic system require non toxic antifreeze like Cryo-tek. Such systems require the water to checked for proper PH balance because the antifreeze will become acidic over time. So give the guys here more information about your current system. Such as it's age.
  • johncarlton7
    johncarlton7 Member Posts: 3
    no picture at this time as i am not at that location system is approx 22 years old and antifreeze is toxic type
  • Docfletcher
    Docfletcher Member Posts: 481
    Get a test kit and see how acidic the boiler water.
  • Firecontrol933
    Firecontrol933 Member Posts: 73
    Is there any radiant heating connected to the system? If so, is the tubing oxygen barrier type?
    Had a system do this once and it was because they had used rubber tubing material in the floors.
  • hot_rod
    hot_rod Member Posts: 15,066
    What type of glycol? EG is ethylene glycol, still commonly used in larger systems, it is more toxic than PG. approved back flow is important and a double walled Hx maybe required for DHW production via indirect or heat exchangers.

    If the fluid ph has dropped into the 7's I would flush, dispose prophet, run a cleaner and start with fresh top quality hydronic fluid. It is a involved task to do properly.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    Does the system actually need antifreeze?
  • johncarlton7
    johncarlton7 Member Posts: 3
    this is the coroaded expansion tank