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cranky Member Posts: 2
Recently I went on a service call with a steam boiler that had two zones of hot water heat. The exspansion tank was leaking bad and completely full. It was an extrol 15. I replaced it without giving it much thought. Afterwards I got to thinking, do you need an exspansion tank in a steam system? I mean there's plenty of space for exspansion. Could I have just plugged it with a half inch plug?

Next Question. Its been a long time since I changed a tankless coil to an indirect. I seem to remember the plumber that i did the job with saying that you have to let the water out of the coil leave a bucket underneath for a little while so pressure doesn't build up. so now i work for another company and my boss just said to plug the old tankless. it will be fine. to me it makes more sense to let it drain out. or cap one side and let the other side drip with a small hole in the end. what are your thoughts?

let me know what everyone thinks. I have lots more q. thanks..


  • Zman
    Zman Member Posts: 7,572
    If the HW loops are open to the steam system then no you do not need an expansion tank. If they are using a heat exchanger or the tankless coil in the boiler then yes.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Alan Welch
  • Jamie Hall
    Jamie Hall Member Posts: 23,421
    On the tankless coil - if it has been deactivated, it should be completely disconnected from the plumbing. I would recommend that one end be plugged, but that the other end should be left open. Why? Two reasons: if it leaks, you'll find out about it. And if it can't leak, but has water in it, the expansion of that water could cause it to fail abruptly. Perhaps no harm -- perhaps a large leak from the boiler.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • cranky
    cranky Member Posts: 2