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general questions

thill Member Posts: 3
hi all.  you all were very helpful to me many years ago when i had a steam system installed.  i actually used your "find a contractor" link to have someone come out and check it out.

i keep getting conflicting info on a couple things and am hoping to get some more expert opinions:

1) my systems (i have 2 steam systems) have never included a main vent - just the vents on the individual radiators.  should all systems have a main vent, or are there reasons there might not be one?  one system has always been very loud (meaning the vents are very loud not banging loud) and i am wondering if that main vent could solve some of that problem.

2) i was told when multiple times that at least once a month, and maybe even every 2 weeks, i should "blow down" the boilers to get rid of all the sediment.  i had been doing it once a month, but started this year doing it every 2 weeks.  i typically drain the boiler until i can't see it in the sight glass anymore, then refill to the proper level (one of them has an automatic feed so it does it for me).  someone is now telling me this does more harm than good because the new water accelerates the rusting of pipes and boiler because the new water is more "oxygenated".

can someone give me some advice on these two items?



  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    Give it a shot anyway...

    Main vents.  You should have them.  You don't absolutely postively need them, but they help a lot.  What happens is that the main vents (near the ends of the mains) let all the air out of the mains, and have a lot of capacity.  This does two things: first, it lets the steam get to all the radiators much more at the same time (not exactly, but much more nearly) and second, it means that the radiator vents only have to cope with the air in the risers and the radiators themselves -- much less air.  So they don't have to work as hard, and are less noisy.  Downside?  You may have to adjust some of the radiator vents down!

    Blowdown -- what is really important with blowdown is the low water cut off and automatic feeder.  There is a blowdown valve at the bottom of almost all LWCO/feeder units.  This needs to be exercised -- I like to do it once a week, but there are differing opinions -- but all that needs to happen is to open in and let it run until the water is moderately clear.  Not drinking quality -- you wouldn't want to anyway! -- but at least sort of clear.  That's all.  On my five section Weil McClain, it's typically a gallon or so.  This gets the crud out of the LWCO/feeder mechanism, so it will work when you want it to.  I personally don't believe in blowing the boiler itself -- using one of the main boiler drains -- down more than once per year.  But that's my opinion.  If you do add more than a gallon or two, it is important to run the boiler up to steaming after you have added the water.  This will purge the oxygen in the water, and reduce any corrosion problems.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • thill
    thill Member Posts: 3
    edited November 2010
    thank you

    thanks.  with my older w-m boiler, it has a blowdown (a black thing that looks like a funnel almost with a open/close lever).  sounds like i have been letting too much out.  i'll just do it until it runs clear and stop.  that one does not have the automatic water feed.

    but i have a newer mega-steam boiler on the other and i didn't understand the difference in the "blow down" vs draining the boiler.  on that one, i was just draining the boiler assuming that does the same thing.  i guess i'll have to look for that valve on the new one.  i don't remember ever seeing it or it's equivalent.  i just hooked up a garden hose to the bottom outlet and let it run.

    but bottom line is, you even do it once a week!  although i am probably making the problem worse by adding so much water.  so you think i can keep doing it every other week??

    thanks also on the tip for the main vents.  i'll look into that further.
  • Sil
    Sil Member Posts: 72

    I think one every week or two is fine.  I do 3 or 4 very quick flushes.  Litterally have the valve open for one second... then close it... then open for one second... and close it... and so on.

    By the 3rd or 4th try its more or less clear.  I only need to add water once every month or two since I am not removing much water.

    The funnel looking thing is where you want to to the flush.  That device is the Low Water Cut Off (LWCO).  LWCO's real purpose in life is to shut the boiler down if the water fell below a certain point (to avoid real damage).  The flushing we are doing every week is to ensure the contacts are clean in the LWCO.

    There is usually a second valve near the bottom of the boiler if one wanted to empty a boiler.  Sounds like that is what u r doing on the megasteam.  There is no need to remove water from that valve with any regularity. 
  • thill
    thill Member Posts: 3
    long term damage?

    have i done any long term damage by draining it?  just curious.  i will stop and try and find the "blow down" on the megasteam. 
  • Sil
    Sil Member Posts: 72

    I dont think you have done any serious damage (then again, I am not a plumbing pro).  Basically what the pros worry about when adding lots of water to a boiler is that little oxygen bubbles will "offgas" and can cause premature corrosion on the inside cast iron of the boiler.  So they suggest as a best practice to bring newly added water to a steam.
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