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Thread: radiator is filling up with water?

  1. #1
    Remodel Contractor GabeS's Avatar
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    Default radiator is filling up with water?

    Hi,

    I have a steam system in a 2 floor house with a basement. It has a dry return. When the heat goes on all the radiators work fine, but one of the radiators on the second floor for some reason fills up with water and starts leaking from some of the joints. While the heat was on I took off the air valve and water started gushing out. I can't figure out for the life of me how water is filling up in the radiator that's on the second floor!! Somebody please give me some ideas so I can fix this myself. I have intermediate knowledge of steam systems.

    The shutoff valve is also new so I know it's not clogged, the water should be returning and the radiator leans slightly toward the shutoff valve for the water to return.

    Congratulations to the person who knows what the problem is and walks me through this one. I have to say I'm a little skeptical. I've already asked half a dozen people and no one could explain this phonomona.

    Gabe

  2. #2

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    Gabe,

    What I know about steam heat fits easily into a thimble so maybe I shouldn't ask this but here goes.

    If the vent on that radiator is working correctly then is it possible that the return line is just plain clogged somehow or that it doesn't pitch the way it needs to?

    I know those radiators aren't easy to remove but if you did remove it you might be able to see what's going wrong there. Provided your sure everything else is working as intended.

    BUT - if the real answer is NO stupid, this is what it is, then that's OK with me because I don't know anything about steam heat but would learn something along with you.

    Sibi
    Last edited by sibi1972; 10-08-2008 at 08:34 AM.

  3. #3
    Master Plumber nhmaster's Avatar
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    One or more of your returns is plugged up.

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    Moderator & Master Plumber hj's Avatar
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    Default radiator

    If there is a trap on the return outlet, it is not working.

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    DIY Hillbilly Southern Man's Avatar
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    To understand where the water comes from you've got to understand a few very simple concepts. The boiler heats water and makes steam (water vapor), which is under pressure so moves up to the radiators.

    When the steam reaches the colder radiator it releases its heat and condenses inside the radiator. In other words, it turns back to liquid water, or "condensate". The liquid fills the bottom of the radiator and drains down the return line. These pipes should drain by gravity back down to the boiler. There should be a pump and check valve to get the condensate back into the boiler.

    Since you have water filling up a single radiator that means that you have a clog somewhere in that portion of the return system. Most likely it is due to corrosion products (rust) or deposition products (lime scale). It depends on your water. If you have hard water it's lime, otherwise it's rust.

    A pro might be able to add chemicals to disolve the crud, back flush the system and clean it out that way. If not its time for disassembly and cleaning. A pro might also recommend treatment chemicals to add to the boiler after its all working again to reduce the corrosion or lime scale build-up in the system.

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    Master Plumber nhmaster's Avatar
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    If your radiators have a trap on the return side the thermostatic disc eventually gives out and needs to be replaced. This element opens when hot water hits it and lets the water return to the boiler either by gravity or a condensate pump. For residential applications, gravity is much more common. To test the trap, fire the system up and feel the outlet pipe below the trap. If the feed pipe to the radiator is hot and the outlet pipe is cold then the trap element is bad. The other possibility is that the wet return pipe is plugged with rust. Very common and typically when they get to that point the pipe is about ready to start leaking and should be replaced. Then again by the time you do all that it may be time to think about converting it to forced hot water and save yourself some money on the old fuel bill. Very few things are less efficient than steam.

  7. #7
    Remodel Contractor GabeS's Avatar
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    there are no trap or pumps on any of the return lines. Just strictly piping.

    It might be a clogged return line on that specific radiator. If so, would that explain that water shooting out of the side when I remove the air valve. Where would the build up most likely be (near the shutoff valve, or first elbow, or could it be anywhere on the line?)

    Also, what are some of the better products used to clean the piping and boiler and what is the best way to go about this?

    I have an old cast iron weill mclain boiler.

    Thanks.

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    When the boiler is on, the heat causes steam which expands, and will pressurize things somewhat. Therefore, when you open up the bleed valve, it, along with the head pressure if the radiator is full, will help to push the liquid out.

    I think you'll have a hard time injecting a chemical into the system to try to dissolve the rust...it will probably release enough that is on the walls of the pipe to create more problems.

    Unless you lose water (in most systems, you aren't supposed to), after a fairly short time, you've reached equilibrium - you've used up all of the free oxygen in the water and deposited all of the minerals, so the pipes won't continue to rust. But, when you have air in there (from leaks or continually having to add water which will contain some disolved O2), rust continues, eventually destroying the pipe. Since rust is larger than elemental iron, when it flakes off, it exposes raw metal, and just keeps going while there is oxygen to allow the process.

    You might have to disconnect that radiator, ream out the rust or replace what has failed, then, if it is still solid enough, re-install it.

    Sounds like to me, if one has reached this condition, it is likely others are close and will do the same. No way to tell how much longer you'll have, but keep in mind, most new systems will probably use as little as 1/2 of the fuel yours currently does. Plus, there are often utility company rebates for updating. I got $1100 back for a new boiler and indirect storage tank from my gas company last year...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Master plumber and Bathtub Befinisher. onezee20's Avatar
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    Either your return is clogged or your water feeder is sticking and overfilling the boiler causing the lines to be filled with water.

  10. #10
    Master Plumber nhmaster's Avatar
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    If there are no radiator traps (and that is fairly common also in residential steam systems) then the return pipe is plugged. There are no chemical products that will clear this out without eating through the pipe. There is a slim chance that only an elbow is plugged but more likely the pipe itself has rusted shut over the years. Unfortunatly when systems reach this stage you will begin having problems all over the house in the near future.

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    DIY Hillbilly Southern Man's Avatar
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    Quote Originally Posted by nhmaster View Post
    ....Very few things are less efficient than steam.
    Interesting I did not know that.

    Quote Originally Posted by jadnashua View Post
    .....

    Sounds like to me, if one has reached this condition, it is likely others are close and will do the same. No way to tell how much longer you'll have, but keep in mind, most new systems will probably use as little as 1/2 of the fuel yours currently does. Plus, there are often utility company rebates for updating. I got $1100 back for a new boiler and indirect storage tank from my gas company last year...
    Both good points. With the price of fuel it will be very easy to justify replacement. Payoff may be a very short time. "Do the math", friend.

  12. #12
    Master Plumber nhmaster's Avatar
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    Undoubtably there will be some that will defend steam heat, but the fact is that you don't get any heat untill the water gets to 212 degrees.

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    Remodel Contractor GabeS's Avatar
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    If the pipes in the walls are rusted shut, then what is replacing the boiler going to do?

    When you say replacement, you are talking about the pipes in the walls, right?

    What kind of test can I do to determine if it is indeed the pipes that are rusted shut?

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    Unless you have a valve or thermostat in that radiator, I think you've already figured out...it's likely time. And, yes, it may be time to bite the bullet and repipe, cleanup or replace the whole thing. Some radiators can be used for hot water systems, or you could switch to baseboard heat, or consider radiant panels or radiant floor heat.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  15. #15
    DIY Hillbilly Southern Man's Avatar
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    Quote Originally Posted by GabeS View Post
    If the pipes in the walls are rusted shut, then what is replacing the boiler going to do?

    When you say replacement, you are talking about the pipes in the walls, right?

    What kind of test can I do to determine if it is indeed the pipes that are rusted shut?
    You could probably convert a steam boiler to hot water but why bother? A new boiler will be much more efficient so will pay for itself rather quickly.

    It seems that you will need to replace the pipes. You can very likely recondition the cast iron radiators though, although it would probably be cheaper to buy some new panels or baseboards. It depends more on style than anything else.

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