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LWCO Clean out or Replace?

justjohn Member Posts: 6
I have a Peerless Boiler with a McDonnell LWCO.  I've always purged the sediment weekly - each time until it runs clear.  Each time the water level in the sight glass would drop and the LWCO would stop the boiler.  I have manual water feed and always keep it with an adequate level.

Last season, I noticed that when I closed the LWCO valve, there would be a trickle flow for a few seconds and then it would stop.  Also, the discharge pipie developed rust on it. 

This year the rust got bad, and I also had this problem the flow was very low when I purged it.  The water level would not drop and the LWCO would only actuate if the level was low (about 1" in the sight glass)  The water color is normal - brown at start and after about 1 quart - near clear.

I called a professional.  I asked if the problem was the rusty discharge pipe blocking the flow of water.  He said the issue is the LWCO is clogged and the pipe is not the issue.  When I told him that I had to clean the pig tail once, he told me to open up the LWCO and clean it out.  Easy job.  Seems he did not want to work on it.

After doing a search and reading the related postings, I still have a few questions that I hope someone can answer. (thanks in advance)

I believe the LWCO is 18 years old.  Does it make sense to open it up and clean it out or should I just replace it?  If I do the cleaning, would I need to replace the rusty discharge pipe too? Or is the rust not an issue?  Are there any reasons behind making the clean or replace decision?

If I'm going to do the LWCO replacement, then I need to drain the boiler....I never drained the mud leg.  1) Am I negligent for never draining the mud leg?   2) If I open the mud leg now...chances are it's clogged.  Is there a recommended way to unclog it? 

So now I'm thinking the whole boiler might need to be flushed to get the sediment out of the botom.  The heating season is about over now so I can do this project.  Should I be draining a cold boiler or warm (not hot) one?  Is a flushing done by filling from the normal water inet and draining a few times?  Or is there more too it than that?  

Going forward, should I be draining from the mud leg?  How often? 

Again, thanks for comments and answers.



  • justjohn
    justjohn Member Posts: 6
    The picture

    did come through so I'm posting it here
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Repair or replace?

    If the lwco is 18 years old, then it and the boiler most likely need some remedial attention.

    The first step in either a replacement is to remove the old lwco, after having removed the drain pipe.

    The valve body can be removed next so the internal float and linkage can be exposed and cleaned. It is possible that you will need some new parts, like the float, in which case the cost of spare parts may come close to the cost of a replacement lwco. If you replace, then it will be more obvious how things go back together, whereas if you repair over a period of time, there may be some confusion in reassembly.

    As for flushing the returns, do you have any drain valves in the returns? Overfilling the boiler first will give you some extra pressure to punch the rusty mud out. When refilling, give the water a quick boil to drive off any oxygen.--NBC
  • justjohn
    justjohn Member Posts: 6


    Thanks for your insight.  Yes I have a small gate valve on the return side, that I plan to use to drain most of the system.  It is probably at the same height as the LWCO but not as low as the mud valve. 

  • Rod
    Rod Posts: 2,067
    LWCO Data

    Hi John-  Attached below is the manual for your LWCO. On the lat page is the recommendation that it be completely disassembled and cleaned annually and completely replaced every ten years. As the LWCO is a very important safety device this device needs one particular attention. While parts are available I would follow the manual and completely replace the LWCO and the drain piping. A new LWCO should be available from your local plumbing supply or your can get them at Pex Suppy on the internet. http://www.pexsupply.com/

    I flush my boiler an wet return annually. While you can flush it when it is still warm you don't want to add cold water to an empty warm boiler as the shock could crack the boiler castings. Allow it to cool before adding water. Cleaning out the mud leg can be a nasty job so prepare for a lot of muddy water. I find a wet and dry shop vacuum is a great help. In some case it may be easier to just go ahead and replace the Wet Return with new piping especially it it is really clogged up.

    Here is a good video on boiler cleaning. http://www.youtube.com/watch?v=q1tw9rz-pUk&feature=share&list=UU7gDszI9COdVbfvJP2YdY5Q

    The video was done by Gerry Gill, who is a very experienced Cleveland steam pro. You might want to take a look at his website  http://www.gwgillplumbingandheating.com/ as he has a lot of good information about steam on there.

    Also you might want to look in the Systems and Resources sections at the top of this page as there is a lot of good information there. Here's an article on cleaning Wet returns. http://www.heatinghelp.com/article/364/Boilers/145/How-to-Flush-the-Return-Lines-on-an-Old-Steam-System

    - Rod
  • justjohn
    justjohn Member Posts: 6

    Wow!  Thanks for taking the time with the details and the links.  I greatly appreciate it.  I was leaning in the direction of replacing the LWCO...just wanted the confirmation and the other general advice....Again thanks.
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846

    You'll find that replacement parts cost a lot more than you'd think.

    I have a used MM 67 with about two seasons on it that you can have for the cost of shipping. (I replaced mine with a probe-type unit, so I have no use for it, but it's too good to throw away.)
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
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