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Boiler cleaning

Need your thought's on this method of "Boiler Cleaning" which I plagiarized from the "Hot tech topics" section, Most importantly the last bit about "Pipe dope leaching oils into the returns".

As an installer with 5 years experience, I read this text as Gospel specifically the "Pipe dope" theory, However my mentor a 25 year certified boiler engineer. Heating and Cooling Supply Shop owner, says I'm cracked regarding the TSP cleaning and the pipe dope thing is just paranoia.

"A good skimming is all ya need and pipe dope don't leach" while berating me for being young and naive as he was the one who brought me into the trade and introduced me to the "Dead men" and their lessons.


We have found the long, tedious and so misunderstood method that works best for us goes as follows:

1) Drain whatever is in the boiler, out. Including the CRP (condensate return piping) and of course, LWCO, if a chamber type (as opposed to a probe type).

2) Fill the boiler to the NOWL (normal operating water level) with clean water. Add 1/2 a cup of real TSP per 100MBTU's of input, preferably dissolved in hot tap water, into the pressure relief tapping with a funnel or into the skim tapping using a full size nipple with turned up ell to get it into the block. Use a whole cup of TSP per 100MBTU, if the boiler is really filthy.

3) Fire the boiler until a horizontal steam pipe ~3 feet away from the riser(s) gets too hot to touch. That implies the boiler is close to steaming. YOU DO NOT WANT TO SHOOT ANY TSPed WATER INTO THE MAINS ! Should that happen, you will be disturbing the mains and all connected piping and radiation of 50+ years of stable "mud" which hurts nothing, and be married to the job because once you loosen the old oxides that were firmly attached to the pipe walls, they will go back into solution and drain back to the boiler, taking months to remove from the low point of the system.

4) Turn off the boiler and drain the condensate return line low point, the boiler block and the LWCO body.

5) After a complete draining, refill the boiler with clean water and setup the skim port with the largest diameter pipe you can, e.g., W/M EG's have a 1½" tap. We stick a 1½ X ~16" blk. nipp. in there. Slowly fill the boiler until the water drools out of the skim tap nipp. into a 5-gallon plastic pail. Fire the boiler. Continue adding feedwater at a rate that would have the 5-gallon pail fill in about 3 minutes. When the drool begins to become violent and spurty, flip the burner switch off and allow the boiler to go back to simply discharging hot water - instead of near steaming. Two pails makes sense. Switch pails so the process is somewhat continuous.

6) Do this until the presence of the "rainbow" effect on the pail's water surface is totally absent. Keep skimming until the water comes out as clear as drinking water. This may take as little as 15 minutes, or as long as an hour.

7) When you are satisfied that no more contaminates are in the block, put a pipe cap on the skim pipe and leave it there for next time this may need to be done.

8) Make the boiler steam or minimally go to at least 180° water temp briefly. This drives off all the oxygen from the new fill. Shut it off. You're ready to put the boiler back into service as needed.

9) It is impractical to skim large boilers. That is not to say it cannot be done, but it is far faster and quicker to TSP the boiler, using the same rate of 1/2 cup per 100MBTU of input, it is obvious a 200 HP boiler would take LOTS of TSP to clean. We found a source of Chinese made TSP that runs around a buck-and-a-quarter a pound.

10) TSP is alkaline. Trace amounts will linger and this is a good thing. We know that when boiler water goes to a pH of 10, virtually all rusting/corrosion is stopped. Anything that raises the pH of the system is a good thing - as long as it does not induce priming & surging or "foaming."

11) As an aside, make sure the pressuretrol never lets the boiler go over 2 p.s.i. Doing so increases the probability of the boiler priming and surging. It also wastes fuel. If it's a vapor system, the operating pressure should be half that, or less.

12) Last "secret." Don't use pipe dopes that are oil based! When heated, the dope softens and will leach the paste "oils" into the piping thread ends, drool back to the boiler and contaminate the water with surface oils that make a clean boiler water, dirty all over again! We have found this process can continue for an entire heating season! As a result, we use teflon tape ONLY on all steam boiler piping. We use the blue, alcohol based "Leak Lok" on the smaller pipes, i.e., gage glass, LWCO, pressuretrol, gage, etc.

So what say you all, is the old man cracked or does the kid have a point?

Bay City MI is where we work and play, A lot of great old buildings with some Amazing Steam Systems and Dan and the Dead Men have been threw them all one way or the other, Its a really cool place to work, however I would like to try my steam luck in New York or Detroit. seems you guys have all the fun.



  • Empire_2
    Empire_2 Member Posts: 2,343
    SOunds like you have the thing figured out.

    There is a product, "at least in the NE where it will be added and allowed to flow thru either Steam or HW systems' Second treatment is to skim the Steam variety after the crap comes back to the boiler where it will settle. For HW there is another Hercule's product strictly used as an additive, containing mostly a Teflon type substance for added protection from harsh residue. Always worked in our boiler applications.

    Mike T.,
  • Big Ed_3
    Big Ed_3 Member Posts: 170
    Another Tip

    Clean the threaded pipes and fittings in a bucket of water and detergent before you dope and install it . Saves you time later....
  • ttekushan_3
    ttekushan_3 Member Posts: 958

    thats pretty much the process I use after acid descaling of old boilers or new piping work. After acid descaling and thorough flushing, the boiler still needs this kind of treatment-just like a new install. Steam output and quality improvements on modern low water content boilers is noticeable.

    I think the cracked old man and the kid are both right. Old boilers with high water content and large steam chests boiled less vigorously for the amount of water surface area they had. Skimming usually did the trick. They were gentle giants--and very tolerant of water quality issues. Modern boilers don't have that advantage and really need to be spotlessly clean for the same steam quality levels.

    [this is also why near-boiler piping arrangements have become critical in recent years. The piping is now doing the steam separator work of the "missing" steam chest area. No matter. The vigorous boil still requires the cleanliness.]

  • James Crosby_2
    James Crosby_2 Member Posts: 6
    Thank you all for your thoughts

    The whole washing your fittings in soapy water gets me laughed off the job site every time but I swear by it, I've gone so far as to wash out 3" pipe before I hang it, the guys at Harrison pipe supply ran me out of their parking lot as I was washing 600' of 3" in their parking lot before leaving for the job, It was so funny apparently they filmed it for posterity as to the foolishness of the "New Guy"

    Oh well, The "new guy" does no call backs either, Time and Karma will prove the Dead Men Right every time, seems maybe you can teach an old dog new tricks it just takes 10 years to do it and by the time I prove my point.

    I'll be the cracked old guy with the old school rubbish floating around his ragged brain and no one will listen to the rantings of a foolish old man, dam you just cant win for losing some days.

    Acid descaling of old boilers or new piping work, thats something I need to read up on. The last old rehab job we did I boiled out a 299,000 boiler for 6 hours loaded with 3/4 pound of TSP and blew it out the vents and let it run to clear out the bottom of the hartford loop returns, really cleaned things up well, however it scared the hell out of the home owners and Acid descaling sounds like a more humane way to clean out them old pipes, with out scaring anybody.

    The system I'm currently working on is an Crown JBF-92 9 section boiler with to spec. dual 2.5 risers to a 3" header properly splitting into 2 3" 80" long runs for a total of 160' of 3" inch mains with a huge 12 rad load split evenly between the runs in an 3500 sq 180 year old queen vic home had to re pipe the entire job from water meter to gas meter the entire house has been rehabbed all starting from a slow water feeder problem for a freind of the family.

    I personally have not seen the light of day for 2 weeks on this job and I just hope it's over soon as its a pro bono kinda thing and the mac and cheese diet has my wife looking at divorce lawers rather seriously lately.

    Till then good luck and have a safe heating season all, Thanks for your time.

    Good Day, James

  • James crosby_3
    James crosby_3 Member Posts: 3
    Squick seems to be the trick

    However the mud leg on the front side wont run clear even after a pound of TSP boiled out through the removed vents and allowed to run to clear out the Hartford loop drain, what is the best way to bottom flush the boiler after all this cleaning? and its only the front mud leg that wont flush clean.

    Crown JBF-92 9 section boiler with all new mains on a 17 year old boiler that was never serviced very well, till now anyways, what are your thoughts on bottom blowing the boiler. How do I scub out 17 years of stuff???
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