Welcome! Here are the website rules, as well as some tips for using this forum.
Click here to Find a Contractor in your area.
If our community has helped you, please consider making a contribution to support this website. Thanks!
How many gallons of skimming
I have a Peerless 63-05-SPRK-SP for a two pipe system.
I skimmed some where between 25-30 gallons. At the end the water coming out was a shade of yellow. I filled two glasses, one with tap water the other with the water from the boiler. I am a first time skimmer. Would we call this sufficiently skimmed? See photo below.
Thank you.
Comments
-
The question isn't the shade of the water — it's whether there is any trace of oil on the top. Hard to see in the photo…
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
1 -
show us where you're skimming from (?)
known to beat dead horses
1 -
The number of gallons is irrelevant also. Its the quality of the skimming and how contaminated the boiler and the rest of the system is. It may take more attempts with less water usage.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System
1 -
I would say your ok. Regardless of what it looks like the test is to run it. While steaming the water in the gauge glass should not move more than 3/4-1" or so.
2 -
-
looks like a nice skimmed water sample to me. How's the boiler running/ What does the sight glass look like?
0 -
Put it in a sauce pan. Boil it. If it foams, you still have oil.
5 -
what fitting are we looking into there? that's not a check in there, is it? it would be holding back the surface oil if is, what's in that port?
known to beat dead horses0 -
Hey @neilc I think you are on to something. It looks like @simon_skove is skimming with the relief valve tapping. There may be an obstruction inside that tapping restricting the oil flow (from other parts of the boiler) to exit out that tapping.
Maybe @ethicalpaul has an opinion, I believe his boiler is similar but smaller. I suspect @ethicalpaul's and @simon_skove's relief valve is on the Left side.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
I don’t recognize the tap layout in the diagram you posted first. Mine matches the second diagram (and seemingly the OP’s photo) where the skim tapping is K (just to the right of the gauge glass). My relief valve is on the side without the controls on it.
25 gallons is a lot of skimming!!
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
Almost looks like a chunk of styrofoam lodged in there…
Could someone explain to me why the directions state to fire the boiler to the point where it "start(s) making steam" which could be interpreted as "boiling" then shutoff and skim? When I skimmed mine I heated it short of making steam and then waited about 10 minutes or so before starting to skim and the water cleaned up with only a couple gallons of skimming. Never had to skim again. Intuitively the oil would want to rise to the top with time anyway. The less time immediately after a boil I would think the less of the oil has made it to the top. Just my opinion.
0 -
I'm not sure what you're saying but I think they say that because when it starts to steam you know the water is as hot as it's going to get. Otherwise they have to try to guess how long to tell people to fire and they have to trust that people will know when the water is hot enough.
Also a little boiling might serve to break up the oil a little bit so it's not all stuck together and stuck to the sides.
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
I'm thinking the agitation from boiling may redistribute some of the oil back onto the walls of the boiler just above the water line being counter productive possibly extending the skimming process. However you want the oil as hot as possible so it wants to move as easy as possible with the water flow to exit the boiler, not put it back on the boiler's walls.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
I could agree with that, except that during skimming, after you do a small amount of boiling, you are going to be adding gallons of water and raising the water level several inches
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
Well maybe it is just me. But bringing the boiler to 211 degrees then adding a bunch of cold water, to raise the water level to the skim tapping, (may be the way the instructions state), but that seems counter productive also.
I'd fill the boiler to the skim tapping then raise the water temperature to 211 degrees.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
That would likely get more oil off the walls.
0 -
the cold water comes into the bottom. The oil is on the top. The oil rises slowly and smoothly up to the skim tapping and is carried out. Skimming!
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el1 -
To me the hotter the oil the better it will follow the water flow, diluting 211 degree water with cold water its not going to stay at 211 degrees very long.
You could skim with a stone cold boiler but how well will it work?
Never done it with oil and water in a clear glass jar, but gasoline and water will settle out almost instantly after shaken up. I can see the oil being thicker and want to stick to the boiler casting so the heat helps it to rise to the water's surface.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
You can skim hot or cold the oil will be on top if the boiler hasn't been run in a while.
You get water in an underground oil tank and its outside and cold the water is always on the bottom. You pump water off the bottom until you hit oil.
Not any different with a boiler but hot skimming is better as the oil loses viscosity. When you skip and add cold water and the boiler is hot it will stay hot for hours the cold water is a small trickle. Even a large commercial boiler I never had to skim more than 45 min to an hour. And I never had to skim more than once. A pencil sized stream is plenty. But I use TSP or washing soda.
1 -
I said it before but you might have missed it. The cold water enters the boiler at the bottom and the hot water and hot oil remain at the top. It works.
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
@ethicalpaul So after heating the boiler water to 211 degrees if you add 25 to 50 % more water to the bottom to raise the water level from normal operation (middle of the sight glass) to skimming level you really think it won't change the water temperature at the top any ???
You probably can skim it cold but I bet it works best when the water is as hot as possible.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
you can do it how you like but the way it’s described in the manuals works quite well. The TSP/washing powder helps a lot too as Ed said
you really think it won't change the water temperature at the top any ???
It's hotter than I'd want to hold my hand under
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
Don't forget you only trinkle in a little water the size of a led pencil
0 -
the skimming is happening at the skim port above the site glass on the same side of the boiler with the site glass. That you are seeing in the inside of the boiler.
0 -
@simon_skove " That you are seeing in the inside of the boiler. "
Well, if it is the back side of that end section that may make the path more difficult for oil elsewhere in the boiler to get to the skim taping to exit.
With some boilers when you look into the Skim tapping you can see all the way to the far side inner wall of the boiler, no inner obstructions. IMO this makes for more efficient path for the oil to exit.
Top view (looking down) of the water line at the skim tapping level.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Once actually skimming.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
I agree with the points made above — it's not how much water gets skimmed. Also, 25 gallons is a LOT.
It's not the color of the water, it's the sheen of oil on top. And just a small amount of oil can wreak a lot of havoc. The evidence is surging, and the measurement is how much the waterline recedes during the call for heat.
As for those who say, skimming is important, and once should be enough, I'm not going to disagree.
With a new boiler, wash out with TSP, drain and refill, then skim — it might be all you need.
If like me, you ran oily water through the system a few times, that means it went all over, and it will take half an eternity to all come back to the boiler, where it can be removed. When skimming properly, the first gallon or two is what really matters.
The first cycle after a skim will tell you whether the oil is gone. And if it gets worse over days or weeks, you know the oil is coming from somewhere else.
For my own sordid saga, where I'm coming up on around twenty skims, go here:
cheers -matt1 -
post a picture of that whole side of the boiler, maybe we'll see something better,
known to beat dead horses0 -
The picture above shows the most of the burner tubes and the height of the flame and the occaisional red tips.
The picture below shows the finish product. The skimming port, to the right of the sight glass is plugged back up.
0 -
How old is this boiler ? I'm thinking it is not new. Was it skimmed when it was new ?
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
it's like this boiler doesn't lend itself to being skimmed, easily, that seems to be the called for port, yet only opens to only the first water jacket, there's no spot there for a domestic coil(?) which would extend thru all jackets, and , , , IDK, what are we missing?
known to beat dead horses0 -
It looks pretty new from here!
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
Here is why I am curious about its age. @simon_skove stated the excessive pressure issue (almost a year ago) was a plugged pressuretrol pigtail, it looks brass to me, even if the original was black pipe, how fast should a pigtail plug up on a new boiler ?
November 2025 " Given that everything looks pretty shiny new, I'm going to guess a new boiler? "
Then looking at what looks like date information on the rating plate. I'm thinking the boiler is over 10 years old, maybe it sat in a warehouse until November 2025, and the pigtail plugged up in a day.
So I am wondering if it was ever properly skimmed after the install, whenever that was.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
That's good detective work on the serial number, but it just looks too new to have been in a basement too long I think.
I will say that if it wasn't skimmed on install, then even a brass pigtail will get gunked up very fast
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
The boiler is a 02/2017 install.
Apparently never skimmed. Then 8 or 9 radiators disconnected and reconnected for finished floor replacement….one radiator move in the kitchen with new piping that was cut and treaded….so until 2025 AFTER all that….there was never any skimming. But at of summer 2026, throughly skimmed…very throughly.
0 -
Well it may not have been originally skimmed or was inadequacy skimmed at that time. The renovation with new piping may have added additional oil to the system.
You have skimmed it recently, I'd see how it performs, you may be done, it may need more skimming, all depends on how it preforms.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1
Categories
- All Categories
- 87.8K THE MAIN WALL
- 3.3K A-C, Heat Pumps & Refrigeration
- 60 Biomass
- 430 Carbon Monoxide Awareness
- 133 Chimneys & Flues
- 2.2K Domestic Hot Water
- 6K Gas Heating
- 124 Geothermal
- 170 Indoor-Air Quality
- 3.9K Oil Heating
- 79 Pipe Deterioration
- 1.1K Plumbing
- 6.7K Radiant Heating
- 397 Solar
- 16.1K Strictly Steam
- 3.5K Thermostats and Controls
- 56 Water Quality
- 51 Industry Classes
- 51 Job Opportunities
- 18 Recall Announcements