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Premature draining

Ive drained my system yesterday for valve replacements and measured the water leaving it with a garden hose digital meter. Does 130 gals sound about right for a 21 unit building on 4 floors?  There are perhaps 50 baseboards and 10 radiators. It seems low and 2 atmospheric boilers.

In any case i want to refill with Fernox after repairs however I'm wondering how long i should leave the pipes empty? I thought repairs would occur today but they have been postponed.

It strikes me that if o2 in water is bad for them then o2 in air may be even worse, no?  Is it safe to leave empty for a few weeks?

Or should i refill asap and drain just before  doing the work? Is there a product other than Fernox that i should use with the fresh water as I'll have to drain again in a few weeks? 

Hopefully not too bad either way....

Thanks for sharing your knowledge and expertise! 


  • Jamie Hall
    Jamie Hall Member Posts: 17,829
    Won't make much difference over a short period of time. Don't bother to refill for a couple of week.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SweatyInToronto
    SweatyInToronto Member Posts: 73
  • Intplm.
    Intplm. Member Posts: 1,345
    It shouldn't be a problem. Maybe leave the boiler laid-up wet during that time.
  • mikeg2015
    mikeg2015 Member Posts: 1,184
    That volume sounds ok since it’s mostly baseboard. The higher volumes are with older cast iron radiators and former gravity systems. I pulled over 100 gallons out of a 2800sqft duplex with just a single 110k Navien boiler.