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Rust in water cause surging?

I have a Dunkirk MODEL PVSB boiler. Its about 12 years old and appears to be installed correctly based on articles on this site.

 I was reading your article on

tuning the heating system were you talked about the causes of wet

steam.  When the boiler is running, the water in the sight glass bounces

up and down about 1.5 to 2 inches.  You called this surging.  I

followed your recommendations on skimming during which I let the water

run through the bpiler for 3 hours and then boiled some where it did not

foam.  The boiler still surges.  When I drain the boiler, the first

half gallon is very brown from rust, and then runs fairly clear.  I

drain it every day with the same result.  Can the rust in the water be

the cause of the surging? 

Also, I have twice drained the return where

there is a lot of rust colored water.  What do you recommend on how to

remove the rust?  Thanks!


  • BobCBobC Posts: 4,861Member
    not usually

    Dunkirks are pretty sensitive to near boiler piping, is it installed per the piping diagram in the install manual, not just the layout but the pipe diameters?

    Old systems can have rust accumulations from a long way back and it takes a long time to get rid of it all. As long as the water from the boiler drain runs clear after a minute or so rusty water should not be responsible for an unsteady water line as long as there isn't any oil in it. A mis-sized equalizer or incorrect hartford connection height can.

    What pressure is the boiler runing at and what are the settings on the pressuretrol? Post pictures of the boiler showing the Equalizer and hartford connection as well as the boiler header.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Hap_HazzardHap_Hazzard Posts: 1,349Member
    edited December 2012
    If you replace the rusty water,

    the water will probably just make more rust by attacking the boiler with any oxygen it can get its hands on. The rust in the water is telling you your water likes to eat boilers. Right now it's full--can't eat another bite--but if you purge it, it's going to sit down for another meal. Check the pH and alkalinity of your tap water--you may even want to send a sample for analysis--and see if it might benefit from some treatment. You want the pH to be around 9 to 9.5 and moderate alkalinity, around 200-300 ppm CaCO₃.

    But this isn't related to the surging problem. Surging is caused by an oily film sitting on top of the water, increasing surface tension and making it hard for the steam bubbles to break through. This makes for a much more violent boil, causing surging, and audible rumble you can hear throughout the house, and wet steam. The cure for surging is skimming. Skimming is usually best performed by a pro, but if you think you're up to it, download this. You'll also need the IOM for your boiler. If the installer didn't leave one, or if it's lost, you can usually download them from the manufacturer's website.

    Now, this is going to require you to completely replace the water in your boiler, so you might as well flush out all that rust while you're at it. The more you can find out about your water chemistry the better. You can raise the pH and alkalinity by leaving a little washing soda in the water after you skim it. Washing soda is recommended for skimming by many boiler manufacturers.
    1983(?) Peerless G-561-W-S
    3" drop header, CG400-1090, VXT-24
  • ChrisJChrisJ Posts: 9,189Member

    I recently learned a lot about this and am very happy with my progress at this point.

    For cleaning I recommend skimming as others have said as well as building a wand for washing the inside of the boiler out.  Have a look at this thread :

    Please this thread regarding water treatment at :


    Its a lot of reading, but I think it will help you a lot. 
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
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