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Proper Cleaning of Steam Boiler

Hello. I have a Weil Mclain Steam Boiler. It is about 30 years old. My question is during the cleaning process, one of the instuctions says to maintain 180 degrees for 2 hours and to not allow the boiler to make steam. Link below.

<a href="http://www.weil-mclain.com/professionals/services/Bulletins/SB0102.pdf">[url=http://www.weil-mclain.com/professionals/services/Bulletins/SB0102.pdf]http://www.weil-mclain.com/professionals/services/Bulletins/SB0102.pdf</a>

Below are Dan Holhan's instructions which seems to me that I shoild allow the biloer to make steam.

There are many opinions on the best way to clean a steam boiler. One of the oldest ways is to dissolve a pound of tri-sodium phosphate (TSP) and a pound of caustic soda (lye) in water and pour it into the boiler. Let it cook for a few hours and then drain the boiler. If you can't buy TSP in your town, try a commercial soap called MEX. It works well and will not damage the rubber gaskets found in some boilers. However, before you clean any boiler, check the manufacturer's instructions for their recommendations.

Are both ways correct? Thanks



  • Rhomar

    I've used Rhomar's products and have been very satisfied with them.


    I like the idea that you don't have to sit there and monitor the operation. You just run the solution for a time and then flush it out.

    Rhomar's techs are very helpful if you have a question.

     Why do you feel the need to use additives to clean  your boiler?  Won't just a good flushing and skimming do the job?
  • George_36
    George_36 Member Posts: 35

    I never heared of this product.  thanks for the tip.

    According to the instructions, I pour 1 quart of Hydro-Solv 9150 in the boiler at the rate of 1 quart per 10 gallons of boiler capacity.  How much should I put to clean the boiler? Should I use the whole gallon?

    Instructions also state to run boiler for several days or weeks until the water becomes noticeably fouled. 

     Does this mean Hydro-Sov 9150 stays in boiler for several days or weeks without flushing the boiler?
  • Boiler Cleaning

    No I wouldn't necessarily use the whole gallon. Usually just one treatment is enough.

    I do several plain water flushings to get the crud out . I also flush "the mud leg" (the wet return) as that seems to be where most of the heavy crud settles. I then treat it once, run that for a week, flush it out, refill with clean water, bring that to a boil and flush that out and then do a final filling. I wait for a couple of days and then see how clean the water is. I then decide if it needs another treatment.  After I'm happy with the condition of the water I skim the boiler.

    One of the important things that you must do is that after you add fresh water you must bring the boiler water to a boil to drive off excess oxygen as the excess oxygen contributes to boiler corrosion.

    Why do you feel you need to use a boiler additive? Sometimes it is better to just leave things alone. Just do a regular freah water flushing.  This is especially true on old boilers. You maybe taking on a lot of work as the additives tend to loosen all the crud in the system and then you may have to do multiple flushing over time to get it all out.
  • George_36
    George_36 Member Posts: 35
    Steam Boiler cleaning

    I read one of Dan's books We got Steam Heat and also read online from heatinghelp,com  that using trisodium phosphate or MEX will clean a stem boiler.

    I also read that if the top of the sight glass is moist or if you can see some droplets of water, while the boiler is working, it means that I have excess oil in the boiler and I will need to clean and skim the boiler.

    Three years ago I added two quarts of vinegar into thr boiler and flushed the boiler and let it run a few times and flushed again. This took about 3 to 4 hours and it the boiler water appeared clear. Now it is dirty again and I it seems that my main vents are clogged, which is why I would like to clean the boiler.

    According to the Rhomar instructions and your previous posts, all I have to do after I flush the boiler, is add 1 quart of Hydro-Solv 9150 into the boiler and let the boiler run regulartly for 1 week and then I flush it out again?

    Rhomar recommends using Boiler Pro™ 903 after using Hydro-Solv 150. Have you used this one before?

    Thanks Rod for your informative posts.
  • Boiler Cleaning

    Yes- that's about it. i put in the 9150 on a Saturday and flush it out next Saturday and then usually use the next three Saturdays to skim. I've used the 903 though probably not as much as I should. I do my flushing at the end of the heating season and that's when I add the 903 to keep things in shape over the summer shutdown.  I generally try to avoid additives.  I've had very good luck with modifying my wet return (Actually i put in a new one of copper pipe -easier than cleaning the old) and have added shut off valves,valves and female hose fittings so I can attach the garden hose  and drains (to attach another garden hose for draining) so I can thoroughly flush the boiler and wet return easily.

    If your vents are clogged try boiling them in vinegar as sometimes this revives them.  If you have any questions on the Rhomar products call Rhomar's tech. support . They are familiar with "the Wall" and are very helpful.
  • George_36
    George_36 Member Posts: 35
    Skimming Boiler

    One week after I use Rhomar, I skim the boiler once per week for 3 weeks?

    Do you know what the steps are to properly skim a steam boiler.

  • Flushing & Skimming

    LOL. Sorry George, I mislead you a bit. I mentioned doing it on Saturdays as that was what fitted best into my weekly schedule! :)

    You can leave the 9150 in the boiler for days or weeks if necessary until it becomes very dirty. ("as long as there is no aluminum present") I just let it circulate in the boiler a week and then flush it out and then follow it with several fresh water`flushings if the water still gets dirty I follow up with another treatment/flushings

    . See the following link for directions :


    I'm not sure why you feel the need to clean your boiler? After you flush just with water`several times doesn't the water clear`up? The general feeling seems to be against putting additives into a boiler as you maybe creating unnecessary work for yourself.  Yes it may clean it up but in loosening gunk and crud in the lines, you may have to repeat the flushing many multiple times to get the gunk and additive out.

    On the steam side of the system the lines are usually quite clear, it is in the radiators and the wet returns where the gunk collects. I mentioned in an earlier post about flushing the wet return. This is usually the area that needs it.

    Skimming - Skimming usually needs to be done only when the system is new or has some work done on it or when indications show  that a skim is necessary. The idea of skimming is to remove surface contaminates, mainly oil, from the water. While flushing may remove some contaminates, oil floats on water`and as the water is drained from the boiler during the flushing, the oil coats the metal sides and remains so you need to flush & skim

    Why is oil a problem? It increases the surface tension of the water and the steam instead of just rising out of the water, has to create large bubbles to break through the surface of the water. These bubbles can be quite large and when they burst, throw a lot of water vapor into the steam stream which is then carried up the riser pipes resulting in what we call "Wet Steam".  With low surface tension the steam bubbles out the water like fizz in a champagne.

    How to skim-  Skimming is just what it says it is, we're trying to skim the oil off the surface of the water. Most boilers have dedicated skimming port in the boiler though you can use any port high in the boiler. Depending on the manufacturer some people use the pressure relief valve port as a temporary skim port.  You can remove the pipe plug in the skim port and attach a pipe nipple temporarily or have a permanent skim valve using a pipe nipple and a ball valve attached to the skim port. If you set up a permanent skim port  I'd also put a cap or pipe plug in the opening of the ball valve to prevent accidents from an accidental opening of the ball valve.

    With the boiler cold, we setup our skim port so that the boiler water can drain out of it.

    I should probably mention that you'll run across suggestions to skim with the water warm but as Dan suggests cold skimming and it makes sense to me. I cold skim.

    What we want to do is add new water VERY slowly to the boiler so that the surface just barely overflows out the skim port. when I say s-l-o-w-l-y , I mean it takes about 2 hours to fill a 5 gallon bucket. When I 've finished skimming I close the port and adjust the waterline to the operation level on the sight glass and then heat the boiler till it makes steam as this drives off the excess oxygen. This is important to do any time you add new water to the boiler as the excess oxygen causes corrosion.

    While I mentioned Saturday mornings for skimming, all you need to do is run the boiler for a short time period to allow any more  oil to work its way to the boiler and then reskim.   The first skim usually takes care of most of the oil though you'll probably have to do  2 -3 skimmings until the boiler water appears satisfactory and settles down.

    Writing all this out has made me rethink a bit and I think I were you I would just flush your boiler several times with no chemicals and then skim.  If  after a week or so the water gets dirty again I'd just repeat the flushing and skimming cycles till I had clear boiler water. Chemicals maybe okay to get the cutting oil from new piping out of a system but I'm not sure I'd use them on a 30 year old boiler. Also it can't hurt to try the multiple flushings first and if after time that isn't satisfactory then you could consider chemicals. It's just that I'm afraid with a 30 year old system, chemicals might cause you more headaches than benefit.

    - Rod
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