Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

How to blow down a boiler

hihi Member Posts: 31
my boiler is about 8 years old and was not maintained, and was not installed properly either! so after reading dans book "the lost art of steam heat" and reading and posting here on the wall i repiped the boiler with a drop header and installed valves for blow down, now I'm just not sure how to blow down the boiler, i put up the pressure to 10 pounds and shut the valves then opened the 2" drain but it still looks dirty, did i do something wrong?? or do i need to do it several times??


  • hihi Member Posts: 31

    Here are some photos, comments welcome!
  • thats a

    That's a hellva drop header setup! Lol
  • Dirty water

    The water in a steam boiler will at best look like weak tea. What must be removed from the water are any oils left over from piping, which can remain for the life of the boiler (shortened as a result of no cleaning!).

    Blowing down the boiler will remove any calcium/rust accumulations, but will not remove any oil, which can only be done by skimming, which removes the surface oil from the water, where the oil remains. Once the skimming has been completed, it will not usually be done again, unless some piping work has reintroduced more oil into the system.

    There are two evils in steam boilers which need to be chased away like the raccoon from the garbage cans-air, and oily residue.--NBC
  • hihi Member Posts: 31
    i first skimmed

    for about 2 hours today and then did a blow down, so I'm aware of the need to skim, i just wasn't sure if the blow down was done correctly because the water still looked rusty.

    i will try skimming again next week (from my understanding you need to do it a few times, correct me if I'm wrong).
  • hihi Member Posts: 31
    Rain in the glass

    It's now 2 days since i skimmed and the upper half of the gauge glass is wet and when it's on you can see droplets of water coming down from the top, so does that mean moor skimming?
  • MDNLansingMDNLansing Member Posts: 297
    Keep going

    I had to skim and drain multiple times on my old boiler. Skimming works well, but you will have oil deposited in other parts of the system that will return to the boiler with time. Start another skim and draw off the first quart of water. Look for oil. If it's there, keep skimming, if not, move on.

    You can use black pepper to check for the presence of oil. Put the water in a jar and sprinkle some pepper on top. If the pepper is evenly disbursed along the surface, you are oil free. If it clumps together or scatters to the outside edge of the jar, there is oil on the surface. Let it sit for 10 mins and look to the bottom. You'll see the heavier oils separate and settle over time. If the water is rusty, just draw a little off the boiler and add some clean water too it to dilute the murky boiler water. The larger the boiler sample the better, but adding clean water to it won't hide the oil that's already in there. It will only make it easier to see with dirty water.
  • stevepstevep Member Posts: 37
    Pepper trick

    Thanks for the pepper trick!
  • MDNLansingMDNLansing Member Posts: 297
    Old Timer

    An old timer taught me that. I was skeptical of this but it really does work. Remember though, it only works on surface oils. Heavy oils that sink to the bottom won't affect the pepper. That's why I suggested adding the pepper right away while the oil is still suspended in the water.
  • Hap_HazzardHap_Hazzard Member Posts: 1,349
    edited November 2013
    Washing Soda

    Are you adding anything to the boiler water when you skim? Some manufacturers recommend using washing soda, aka soda ash or sodium carbonate (not sodium bicarbonate or baking soda).

    By the way, your header looks a lot like mine before I put the insulation on, except the drop is bigger. Keep an eye on those riser unions. If those swing-arms are swinging they can loosen up, so make sure they're tight every fall.
    1983(?) Peerless G-561-W-S
    3" drop header, CG400-1090, VXT-24
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!