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To Flush or Not to Flush Oil Fired Steam Boiler

Karena Member Posts: 1
edited January 2021 in Strictly Steam
2 weeks ago had a new install of oil fired steam boiler (Williamson OSB-3 2 Series) What is the homeowner's responsibility to do to keep system functioning correctly and avoid problems with heat, hot water and warranty? Kind of afraid to touch anything. The manual does not clearly state if flushing is necessary or if so, how often or how to do.
It has VXT auto water feeder and , tankless coil and Probe type LWCO. Previous boiler was only 13 yrs old (New Yorker) and had manual water valve. Tank became corroded and leaked even though I had it serviced "tuned-up" each year.
Not sure what went wrong.


  • EzzyT
    EzzyT Member Posts: 1,295
    What was the overall cause of failure on the previous boiler?
    Hopefully the boiler was sized and installed correctly. 
    E-Travis Mechanical LLC
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    Very much agree with @EzzyT 's questions! But in a slightly more direct answer to yours, the three most important things you, as the homeowner, can and should do are to make sure that if there is a float type low water cutout that it is flushed occasionally, to make sure the float is free, and to keep track of the water usage -- and to have the boiler cleaned and serviced by a competent technician, with the necessary tools and instruments and the knowledge to use them, once a year.

    13 years is actually not an unusually short lifetime, but tracking the water usage will indicate whether or not you have some leaks -- which have to be addressed, as too much fresh water can cause a premature failure.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Karena
    Karena Member Posts: 1
    The previous boiler's tank was completely corroded on the inside once the top was removed we could see all of the rust and holes. Not sure if it has been serviced each year with previous homeowners. For past 4 yrs I had it serviced but I realize now that the companies only serviced the burner and never checked for leaking inside the tank. Now I am uncertain if I should be turning valves to let out any "dirty" water and then allowing the automatic water feeder to replace it as needed. If so, how often should I do this? Is it only once annually with a service appt?
    Also, if the installer said he "skimmed" the new boiler at the time of installation-is that adequate? One and done?
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    The annual service should include cleaning -- brushing and vacuuming -- the entire fire side of the boiler. This takes a little time; more on some than others. That is in addition to cleaning and adjusting as needed the burner.

    On flushing. Probably not a bad idea, once a year, to open the boiler drain valves and flush some of the grundge out of the bottom of the boiler, but there is no need to drain it completely. if you do that, bring it right back up to steaming and run it or an hour or so total to get any air out of the water. If you have a float type low water cut off, it's a very good idea to blow it down once a week (do as I say, not as I do...) again to get the grundge out of it. If the boiler is running, doing that should shut off the boiler, and the automatic water feeder should refill properly...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • KC_Jones
    KC_Jones Member Posts: 5,739
    Boiler performance will tell you if one skim was enough. Wait a couple weeks and watch the sight glass while it's firing, if it's only bouncing about 1" max you should be good. Any more than that and it's probably surging and needs more skimming.

    You shouldn't need to flush the boiler except maybe once a year to make sure the valves are all flowing freely. Excess make up water is usually what kills the boilers, with the VXT you can track water usage so you don't have another premature failure. For reference you should use about 1 gallon per month max on a boiler that size.

    There was someone on the forum within the past few weeks asking what should be done for yearly maintenance.

    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • AdmiralYoda
    AdmiralYoda Member Posts: 629
    Have you ever had your water tested? The lower the pH, the faster it will corrode the boiler. Hard water and all that stuff matters too.

    I have municipal water and my pH is 7.5, which is pretty good. I add 8oz of Rectorseal 8-way to the boiler to get my pH to 10 which is what my boiler recommends. Corrosion stops with a higher pH, though too high a pH also has its own problems.

    I have a float LWCO and without Rectorseal 8-way if I drain a bit every week it is sludge. When I use the Rectorseal there is no rust in there whatsoever.
  • nicholas bonham-carter
    The manual should show where the skimming piping has been installed, and how to do it. Several sessions will be necessary of several hours each. Chemical additives cannot substitute for this most important procedure.
    I would turn off the water leading into the auto feed, to get an idea if there are any leaks elsewhere in the system, such as from buried returns. Test the LWCO before this.
    Post some pictures of the boiler, and it’s piping for more advice, and observations.—NBC
    EBEBRATT-Ed Member Posts: 15,544

    What will kill a steam boiler is adding fresh water over a long period of time. When you add water you add oxygen which is bad.

    No harm in flushing and draining and refilling once a year.

    Keep an eye on your VTX feeder. If you see this thing adding water all the time you have to get someone in there to find and fix leaks. Keep a record of the water usage.

    Steam leaks may not be seen but that is still water loss