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Water Level on Steam Heat Boiler Fluctates

Hi, I recently moved into a house with a gas-powered steam heat boiler. I've been told that I need to periodically add water to the boiler keeping the water level near the optimal water mark on the sight glass. My issue is: do I fill it to the line when the boiler is on or off? Earlier I went down to check on the water level and it was at the optimal mark (the boiler happened to be off). Then, an hour later was in the basement while the boiler was on and the water was way below the line, nearly at the bottom of the sight glass.

I'm worried that if I fill it while the boiler is on, it will put to much water into the system causing bigger issues. Any help on this is much appreciated! Like I said, this is a whole new system for me.


  • Jamie HallJamie Hall Member Posts: 12,718
    Let's see here. First off, "periodically" should mean a gallon per week or less. If it's more than that, find the leak...

    Second, if you are filling manually, it should be done with the boiler off, and waiting 10 minutes or so for any condensate out in the system to come back to the boiler. That way you won't over fill.


    Third, if the system is dropping from half way up the sight glass to almost at the bottom, there may be something amiss with the near boiler piping or the condensate returns. Can you post some pictures of the boiler, showing the way the piping is arranged around it?

    Fourth, if your pressure is too high, that can force water out of the boiler. The pressure should not be more than 1.5 psi cutout and 0.5 psi cutin.

    Fifth, is there a low water cutoff control on the boiler? Where is it in relation to where you found the water when the boiler was firing?
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Will the water level return to half way up the sight glass after having been off for 20 minutes? If not, then how long will it take?
    The wet returns of the boiler may have become plugged up slowing the return of the water, or as Jaimie says, the overly high pressure may be forcing water out of the boiler, stacking it up into the returns. Does the gauge show what the pressure is while steaming?
    Is there a testable Low water cut off, (LWCO) on the boiler, or an electronic type. The first one must be blown out weekly by opening the valve on the bottom, and the second type should be checked for function by lowering the water level to see if it works, during the annual maintenance.—NBC
  • qwilliamsonqwilliamson Member Posts: 4
    Thanks Jamie and Nicholas. I don't think there is a leak. I have only added water once since turning on the heat in November. I'm attaching some photos that hopefully will help with the other questions. It's dark here now so they're not the brightest, but hopefully you can make out the important parts. I'm not sure if there is a a low water cutoff control on the boiler- can you tell from the photos? Photos were taken while the boiler was on.

    The water in the sight glass does return to half way once the boiler is turned off and it only takes a few minutes of it being off for this to happen (less than 10). Thanks!

  • Jamie HallJamie Hall Member Posts: 12,718
    Looks good and sounds OK -- except two questions. Why is the cover off of what I suspect is an electronic probe type low water cutoff? Is there a reason?

    And -- on the box with the clear cover at the top, what are the settings on the two scales? I can't quite make them out.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • qwilliamsonqwilliamson Member Posts: 4
    When I moved in there was no cover on the box. I’ve already asked a plumber to order it’s on it’s way. Here’s an up close photo of the top box
  • Jamie HallJamie Hall Member Posts: 12,718
    Looks like you're good to go -- those pressure settings are fine.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • FredFred Member Posts: 8,418
    edited December 2017
    @qwilliamson , the box without a cover is your low water cut-off. Also, it looks like the boiler water is really dirty. Has the boiler ever been skimmed? It looks like a fairly new boiler and many times the installers don't skim them like they should. I would drain the boiler, flush it out then fill it back up and skim it or have your service tech skim it and show you how to do it for future reference. It has to be skimmed to remove oils from the surface of the boiler water. Draining won't do it for the oils. They will just cling to the sidewalls and float on the surface again when you fill the boiler. Skimming is important because when oils float on the surface of the water, it makes it very difficult for steam bubbles to break through and that alone will cause the boiler water to back out into the returns, until the end of a heat cycle. Burnhams seem to be more sensitive to oils than some of the other brands. I have a Burnham also, 35 years old and anytime I even change a small piece of pipe on the system, that introduces enough oil that I have to skim to stabalize the water again. Once you do one or two good slow skims, I think you'll see an immediate difference.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,945

    The installer could have done a better job piping the boiler (and there are others on here way more picky than I). Can you post the model# of the boiler I suspect some of the piping is undersized?

    Also look for an air vent on the end of your dry return. I don't see one in the picture but it may be there.

    Also, what I really don't like is the equalizer connection from the header. The elbow should turn straight down before going horizontal.

    Also the boiler is building pressure which I don't like in a house job.

    The water level dropping so much seems like undersized piping and header could be sucking water out of the boiler.

    Not looking for problems we see may jobs worse than yours but there is room for improvement and smaller fuel bills.

    If the boiler manual is there look at the piping requirements for your model boiler and compare it to what you have.

    1 1/4 pipe is about 1 1/2 od
    1 1/2 pipe is about 2" od
    2" pipe is 2 3/8 od
  • qwilliamsonqwilliamson Member Posts: 4
    Thanks all. Who would be the right person to teach me how to do a skim? Is this using Rholmar or a similar chemical? The installers of the boiler seem to be expensive and busy- is this something a plumber could do?

    The boiler is a Burnham Independence PV: IN_PVSNI_
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,945
    edited December 2017
    Anyone who can read and follow the directions can do it. Some use no chemicals. Some use TSP and some use TSP and lye.

    1 lb / every 50 gallons of water in the boiler. You will have to look up your boiler to find he water content.

    and you need a skim tapping on the boiler

    Personally I would use just TSP first and try that but that is just me.

    basically what I do is put the chemicals in the boiler after mixing with water in a pail first and pour it in the boiler.. (use caution eye protection and rubber gloves) Add through a spare tapping. You may have to remove and reinstall the safety valve to pour the chemicals in

    Run the boiler until it is hot but shut the burner off before it makes steam.

    crack the skim tapping open and add feed water (just a trickle) you only want flow the size of your little finger coming out the skim tapping.

    Let this run for an hour or so. Drain the boiler. When the boiler is cool enough to touch with your hand refill the boiler with water. Drain the boiler and refill again. make sure the safety valve is back on , button up the skim tapping and start it up.

    It's a bit of work but can make a huge difference
  • FredFred Member Posts: 8,418
    edited December 2017
    On the back side of that boiler should be a skim port, above the water line. It should be next to the Pressure Relief valve (PRV) and should be a 1.25" nipple with maybe a valve or cap on it. If it's not there, then you may have to use the 3/4" tapping that your PRV is screwed into. Take that PRV off, screw a 3" or 4" nipple into the boiler, screw a Tee onto that nipple and remount your PRV onto the top opening of the Tee and put a plug into the end of the Tee. That tapping isn't ideal but it works. That's what I have to use when I need to skim. Because it is only 3/4", you have to skim very slowly. Look in your owners manual and it will tell you how to do it but it is very simple. DO NOT ADD ANY CHEMICALS.
    - Shut the power to the boiler off and let it cool for a half hour
    - Drain the boiler to get rid of that dirty water
    - Fill the boiler back up again and drain it one more time to get rid of the residual crud
    - Fill the boiler up again, to the normal water level and power it up and let it run until it starts to steam
    - Shut the power off and open the skim port
    - slowly manually add water to the boiler until water starts to come out of the skim port.
    - Dial the manual feed down until the stream of water coming out of the skim port is just a trickle. Smaller than the diameter of a pencil. I normally then connect a garden hose to the skim port and run that over to a floor drain. Let it trickle like that for two or three hours. Weather permitting, I normally allow it to trickle into the floor drain over night. Again, keep the flow down to just a trickle. The goal is to have the flow so slow that it doesn't disturb the water at the the surface. You want that surface water (where the oil is floating) to just slide off and out the skim port.
    - When done, shut the manual feed off, put the cap/plug back on the skim port, lower the boiler water level back down to its normal level and start the boiler.
    - You are done

    On a different note,Do you get any water hammer when the boiler is running? I do see that the installer put a bushing into the header and then installed a smaller elbow on the equalizer (pipe that turns to the left and then turns down). That bushing will allow water to pool in the header and can cause some hammer. That bushing should be taken out, a full size elbow installed and turned down. Then a reducing elbow installed and carried over and reconnected. You always want steam pipes reduced on the vertical, never on the horizontal where they can hold water. It looks like a fairly simple correction.
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