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dirty steam boiler

wiley Member Posts: 16
Hi All -

Long term lurker here. I have a recent issue with my steam boiler and am hoping to get some advice. I have an 8 year old burnham IN4 steam boiler. It had been working very well until.......

late last spring I replaced all my cast iron radiators with new ones as part of an overall renovation. I worked with a plumbing supplier to properly size them so they matched my old system. There was a lot of banging, cutting and re-threading of return pipes so they would match up with the new radiator heights. So when the system was re-started everything was fine for a day or so and then my main vent started spewing rust water and radiators were not getting hot. I surmised that all the banging and cutting in addition to the machine oil in the new rads, got dumped into the boiler and that the water/steam was contaminated with rust, sludge and oil. I had my plumber put a skim port on the boiler and I began skimming - and skimming and skimming. 7 days 5-6 hours per day. There seems to be some debate as to whether this should be done cold or warm, to cover my bases I alternated one day hot one day cold.

I also emptied the water in the boiler a number of times in an effort to clear out the sludge but I am reluctant to do this too much as I know adding new water frequently is not good practice for a steam boiler.

So despite my efforts the problem persists - with new water I can get 2 -3 days of good operation and then my main vent starts spitting again (and it is a mess) and my radiators go cold. At this point the water in the sight glass is dark rust and the glass itself needs to be physically cleaned with a pipe cleaner to get the debris off.

Does anyone have any suggestions as to how best get my boiler clean? I can continue to skim if need be but I am surprised that all of my efforts in that area have had minimal effect. I'm reluctant to use any type of chemical treatment but am starting to consider it. I'm in Queens, NY so our water quality is generally good. Any thoughts would be appreciated -


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,818
    edited December 2022
    8 WAY is used for boiler cleaning. there are several instructional videos on YouTube for this. Then try a process called Skimming (also on YouTube). The oil in the steam boiler (If Any) will stick to the sides as it floats on the surface while the water is drained out. You need to skim the top of the water from the "Skim Port" if you have one (or you will need to make one) to get the floating grunge out of the boiler.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Jamie Hall
    Jamie Hall Member Posts: 23,270
    While you are at it, check every single one of the pipes -- new or old -- for correct pitch. Easy to get things just enough off.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,510
    Best way to skim is to add 1 lb of TSP/50 gallons of boiler water. You will have to find your boiler water content and adjust TSP accordingly. Mix tsp in a bucket with hot water and with the boiler shut down add it to the boiler through the skim tapping (with an elbow and nipple added to it} Close the skim tapping and run the burner until the header is hot. Shut the burner off and start skimming. The flow coming out should be the size of a lead pencil. Add water slowly

    A couple of hours should do it

    When done and after cool drain the boiler and refill drain again and run. I have never done one this way that did not work afterwords
    Long Beach Edethicalpaul
  • BobC
    BobC Member Posts: 5,477
    You could also use a wand to clean the boiler. You build the wand with a capped length of copper pipe with a valve (very small holes drilled into the sides of the pipe that will forcefully spray water against the inside of the boiler casting) that you insert through the skim port. Feed this with washing machine hose and feed hot water into it, wear gloves so you won't get burned. This video shows someone using a wand to clean out the bottom of the boiler, you will be going into the skim tapping to get the oils off the top and sides of the inside -
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • wiley
    wiley Member Posts: 16
    Thanks for your thoughts on this - the wand idea is pretty interesting. The way my skim port is set up it looks a bit difficult to open up - any suggestions for another way in? I was considering using the safety valve as a way to gain access.