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Water Gauge Problem

mhj Member Posts: 10
I have a Dunkirk Steam boiler only a few years old. This season its been giving me some problems. The low water cutoff keeps shutting the boiler down and I need to a add a little bit of water each time to get it started up again. I thought it was a problem with the gauge so I kept both the top and bottom values on the gauge open, see the picture below, but after each time it fires up, the water level in the gauge falls down half away and the boiler won't start up again until I add some water, only a little, and the level in the gauge goes up. Then it fires right up until next use.

Any idea what could be causing this?


  • Rod
    Rod Posts: 2,067
    Boiler Problems.

    Hi- First of all, the valves at the top and the bottom of the gauge sight glass should be both OPEN at all times especially when operating the boiler. These valves are just for use when it is necessary to remove the glass tube for maintenance.

    You either have a leak or a slow return. The next time the low water cut off shuts off the boiler, don't add any water and lets see if over time say 30 minutes or so the water level in the sight glass returns to its normal level. If the water does return to its normal level this would indicate that you have a "slow" return which probably means you wet return needs to be flushed.

    Have you had a pro look at your boiler lately?  Also It might help if you give us the model number of your Dunkirk and posted some pictures of the boiler that the piping attached to it. Take the pictures from far enough away from the boiler so it includes the piping.We can blow the pictures up if we need more detail.  Do you have any steam leaks from valves, vents or piping  on your system? Do any of the steam pipes run underground?

    - Rod
  • mhj
    mhj Member Posts: 10

    I have left both values open but the water level still drops. I have also left the boiler alone and it won't start up again, especially problematic in the morning. Have not had a pro look at it but I am tempted to if it keeps going on like this. I have not noticed any types of leaks anywhere in the system and no pipes run underground.

    Boiler Model No. PVSB-5D and I was able to get the Installation manual for it.

    Thanks for the help and I'll put some pictures up soon.
  • Rod
    Rod Posts: 2,067
    Sight Glass

    Hi- What we are interested in finding is after the boiler stops and then is left alone (not operating)  for a while (30 minutes or so) does the water level in the sight glass rise.?

    If the water is s-l-o-w-l-y returning to the boiler it will slowly rise in the sight glass.

    - Rod
  • mhj
    mhj Member Posts: 10

    No, it doesn't seem to rise at all. After each time it fires, he level goes down to about half way until I add more water. Its also strange that I only need to add a little bit of water for the gauge level to go up and the boiler to start up again.
  • Jamie Hall
    Jamie Hall Member Posts: 22,899

    the water goes down in the glass to half way (which should be above the LWCO level), and stays down, either you're losing that much water or something else is happening.

    My inclination is something else, and the first something else I would look at is the connections from the boiler to the gauge glass and the LWCO.  Are they clean and open?  Does the LWCO share the connections with the gauge?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mhj
    mhj Member Posts: 10

    All the connections seem to be clean and open. The LWCO seems to connected on the top part of the gauge. Please see the pictures for a better description.

    Also note the water level in the gauge, it usually drop down to about the blue marker line after each use.
  • crash2009
    crash2009 Member Posts: 1,484
    What is

     that green colored pump for?  
  • Rod
    Rod Posts: 2,067
    Leak Problems

    Hi - You really need to get a pro to look at your system. There are a lot of things that could be causing your problems.  Your boiler piping configuration and pipe sizing leaves a lot to be desired, Take a look in the installation manual - Page 5 to 7 and especially look at Fig 5 on Page 5, observe  the configuration, the required fittings ( you have no tee for skimming) and pipe sizes . These are the “minimum” specifications that need to be followed for successful operation. Your system has no header and no equalizer and from what I can see the equalizer and boiler piping are of too small size wise. You also seem to have a circulating pump attached to the boiler which could be a possible source for problems.

        I’ve attached a drawing from the boiler manual. You will see that the boiler’s design waterline (cold) is 24 inches above the floor. The first thing I would do is check and see if you are filling the boiler to the proper level. You will also notice that the boiler’s design Waterline and the Low Water Cutoff water level (drawn in blue) are very close. which would mean that even with a small leak it would affect operation.

    The first thing to do is to decide whether this is an actual leak ( permanently losing water from the system) or whether the water is “hiding” in the system. The fact you are constantly adding water would tend one to think you do  have a leak somewhere. I would check all vents , Main and radiator and all valves. I would also carefully check the system to which the  circulating pump is attached. Be careful not to check for leaks with your bare hands! You can get a bad burn from a steam leak! Use a strip of newspaper, hold it by one end and use the loose end to check around the vents and fittings. Movement in the pare indicates a steam leak.

     You need to find and fix the problem. Constantly adding water to the boiler can cause accelerated corrosion due to excess dissolved oxygen in the “new” water. You always should bring the “new” water to the boiler to help drive off the excess oxygen. If you can’t readily determine the source of the leak I would get pro to take a look at your system..

    - Rod

  • mhj
    mhj Member Posts: 10

    Thanks for the help everyone. I guess I'll just have to call someone in and take a look at it. I just don't have the time or the needed skill to tackle this one.
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