Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Is there a leak in my heating system?

This is a historic house with an oil-burning hot water heating system. The boiler itself was replaced within the last 10 years, but the pipes and radiators probably date to the 1930s.

About a month ago, the system completely stopped working. The technician from the heating company said that the pressure had dropped to zero. He bled off a ton of air and refilled the system. (He also reinstalled the circulator pump, which he said had been installed upside-down, but I gathered this was not a major cause of the problem.) He said that the problem was due to a clogged water feeder valve.

Since then the heat has worked, but there are still some problems. With the recent cold weather, I have had to bleed certain radiators every day just to keep them hot. I hear frequent bubbling sounds in the pipes. And there is one radiator (the farthest one from the boiler, as it happens), that never gets warm. I bled that one until air stopped coming out, but no water came out.

Now that I know where the pressure gauge is, I have been checking it, and it is steady at 10 psi. I was told 12 psi was the standard, and one web site I found claimed that higher pressure than that is needed for a big house, which this is.

I am not an expert by any means, but I suspect water is leaking out of the system. I have seen no signs of water damage, but perhaps there are many small leaks. I called the heating company again, but this time they just advised me to call a plumber.

Anyone have any advice? Thank you.


  • SWEI
    SWEI Member Posts: 7,356
    Turn off the auto-fill

    and see how long the pressure holds.  That will tell you if you are leaking water.

    Size of the house does not matter, but height does.  Take the vertical distance between the lowest and highest points in the system, multiply by 0.434 and add 5 PSI.  That is the minimum fill pressure generally needed.
  • icesailor
    icesailor Member Posts: 7,265
    Bleeding air from radiators:

    If you bleed air from a top floor radiator, you get air and then it stops venting air but no water, you do NOT have enough pressure in the heating system. When the system doesn't have enough pressure, and it heats up, the water will expand and create pressure. When it cools down, it contracts. When it contracts, it will cause negative pressures inside the closed systems on the upper levels, sucking air through leaking valve stems and automatic vents. It can appear the system is loosing water. Raise the pressure to a mini,u, of 18# if it is a two story old New England house with a boiler in the cellar.

    If the system actually dropped to zero and you say the gauge at Zero, you probably have a leak, but did you see it? Why didn't the tech try to find the leak? There's other issues.
  • NotHaunted
    NotHaunted Member Posts: 4
    edited January 2014
    Tall house

    I did not actually see the gauge at zero. That's just what the tech told me.

    The house is actually three stories high at the tallest part, with the boiler in the cellar.

    Edited to add: I would guess there is about a 30-foot vertical distance between the lowest and highest parts of the system.
  • bustoff315
    bustoff315 Member Posts: 26
    Raise boiler pressure

    Keep the boiler pressure up around 20 PSI while you go around the house and bleed each radiator. The boiler feed valve is likely factory set for 12 PSI so you will have to lift the manual lever to get the desired pressure. After you bleed the last radiator make sure the boiler is around 18-20 PSI and then check the gauge every so often to see if you are losing any pressure.
  • icesailor
    icesailor Member Posts: 7,265
    Setting system pressure:

    But there is a way to overcome the factory pressure setting if it has a "fast Fill" feature. After you use it, and you need to set it at 20#, you have to manually adjust it. There's a procedure to it. The Tech that came and said it was at "Zero" should have set it.

    If you look on the pressure and temperature gauge (a Tridicator Gauge because it gives you three readings), notice that there are two scales where the pressure needle travels. On side is in Pounds Per Square Inch (PSI) and the other is in feet of altitude or how high the water level is above the gauge for the corresponding boiler pressure. If the gauge pressure says 10#, the water will be 23' above the gauge. I always use 8' for a cellar, and 10'+ for each floor. If radiators are on the third floor rather than baseboard, I add 5' for the height of radiators on the top floor as a basic rule of my big thumb or 43' of height or altitude. or 18.6 # If you have a compression tank over the boiler, it is probably water logged.

    If you can't figure it out, you need a professional. If you have a bladder type tank and radiators, it isn't big enough. If it is a cold start boiler, and has a bladder type tank, it REALLY is too small. Have another tank added. And replace the fill valve. It sounds like it isn't working.
  • NotHaunted
    NotHaunted Member Posts: 4
    It's clear I need a professional

    I have a compression tank, but it sits on the floor next to the boiler, not over it. Would that prevent it from working?

    I am definitely going to look for a qualified professional. Thank you for your help.
  • SWEI
    SWEI Member Posts: 7,356
    Finding a professional

    Has become unfortunately challenging in our so-called modern world.  Where are you located?
  • NotHaunted
    NotHaunted Member Posts: 4
    Harford County, MD

    Northeast of Baltimore.
  • SWEI
    SWEI Member Posts: 7,356
    If they're not too busy fixing steam systems

    You'd be well advised to consider http://www.heatinghelp.com/professional/79/All-Steamed-Up-Inc