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Boiling Water In Vertical Pipes

Dr_AculasDr_Aculas Member Posts: 6
I have a hydronic heating system. (Baseboard radiators with copper pipes and aluminum fins). I can feel and hear water boiling in the vertical pipes going from the 2nd floor headed to the 3rd floor of the house. Its an old house and previous owners have painted over the vertical pipes. I have lowered the aquastat to the lowest setting and i can still feel it boiling. Can anybody help me with this? Is it dangerous and if so, how can i fix it. Thank you.


  • Jamie HallJamie Hall Member Posts: 13,108
    There is no way the water should be boiling in the pipes -- if it is.

    First, check the pressure in your system. For a three story house, it should not be less than 20 psi cold, and shouldn't rise much when the system warms up -- perhaps to 25 psi.

    Second, check the temperatures at which the boiler is running. The boiler should shut off at not more than 180 F.

    Does the third floor heat properly?
    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
  • SuperTechSuperTech Member Posts: 1,383
    edited February 8
    If water is actually boiling (I highly doubt it) you have major issues.
    What you might be hearing is likely either expansion noises from poorly installed piping, or air. I bet it's expansion noises. This would sounds like popping and pinging right after the boiler first starts circulating hot water. It usually stops after the system has been circulating for a few minutes. Or maybe you have noise from air in the system, but I don't know how that would be mistaken for boiling, but it can cause noise.
    Why do you think it's boiling? What is the aquastat high limit set to and how hot does the tridicator gauge show the boiler water getting before the burner shuts off?
  • ch4manch4man Member Posts: 221
    sounds like your system needs to be purged of air. you stated you can feel it boiling. that temperature will burn your hand in short order.
    if your unsure on how to purge the system of air please post a picture of the boiler and near boiler piping from far enuf back so we can see all the near boiler piping and we can assist
  • Dr_AculasDr_Aculas Member Posts: 6
    No it is boiling. I grab the hot vert pipes and i can feel it bubbling non stop all night until the heat is shut off and it cools. The expansion noises i know. Its a creaking and popping sound somtimes. But no it is bubbling like crazy in the vertical pipes leading to the third floor. When i grab it you can feel it bubbling like crazy and vibrating from it. I dont know if it has something to do with most of the baseboard radiators are either behind a bed or covered by furniture, or just collected dust so the aluminum fins arent dissipating the heat properly and cooling it down as it travels through the horizontal pipes or what. Thats the only thing i can figure. I turned the honeywell aquastat to the lowest setting which i believe is 170 but its still doing it just not as much. But the aquastat is making a buzzing noise now. Thanks for your help.
  • mattmia2mattmia2 Member Posts: 1,619
    If the system doesn't have enough pressure it could boil at the high points. it will also likely cavitate at the pump if those temp/pressure conditions exist.
  • neilcneilc Member Posts: 809
    I don't think you would grab a boiling pipe long enough to feel the boil,
    this really sounds like air in the system.
    what pressure do you see at the boiler?
    if you shut it all off, the circs also, do you have a rad vent on the 3rd floor? where you could check for static pressure?
    you get water out up there, correct?
    and then if you do, at the boiler, are you pumping to, or away from the expansion / compression tank ?
    could you post a picture of the boiler, piping, circ, and tank ?
    one large distant picture showing all?
  • Jamie HallJamie Hall Member Posts: 13,108
    Well... you say yo know boiling when you hear it. OK. Now, however, if your pressure is low at the boiler, it could be below atmospheric up higher in the system. It could even be low enough so you could, in fact, get boiling -- but at a much lower than the nominal 212 at atmospheric.

    So... what is the pressure at the boiler at the intake to the pump?
    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
  • mattmia2mattmia2 Member Posts: 1,619
    Especially if you have some sort of restriction, but the place to start is with the temp and pressure on the gauge on the boiler.
  • Dr_AculasDr_Aculas Member Posts: 6
    Yea let me get a picture of it. Ill post it. But trust me i understand what you mean about not being able to grab it long enough but whoever had this place painted the pipes like 3 times so theres a layer of paint protecting the actual pipe but its really f*in (excuse my language) hot and i can grab it for about 1-2 seconds whichnis enough to feel it boiling. Now after the temp was turned down on the aquastat, its a crackling sound. Like if something it hot and youre dripping water on it and it sizzles you know...? And its humming also. Next time it is ill record a sound file also because maybe you guys can help me. My wife is frightened of it. I am too a little bit. But ill get a picture and post it asap. Thank you for all your help. I really do appreciate it.
  • mattmia2mattmia2 Member Posts: 1,619
    Did we ever find out what the pressure at the boiler is here?
  • mikeg2015mikeg2015 Member Posts: 1,178
    edited February 16
    Probably its high water velocity and some air in the system. If it was boiling in the piping it would HAMMER as it flashed to steam.

    I know that sound. I know when it’s time to clean the strainer protecting the the pump on my indirect water heater piped to my steam boiler. It’s makes a “pop, pop, pop” sound.

    You can hold any pipe over about 160F. Copper especially.
  • Dr_AculasDr_Aculas Member Posts: 6
    Heres a short video of the crackling sound. Sorry i was away for a few days. But u can hear the crackling. I will get a better vid with a mic
  • Dr_AculasDr_Aculas Member Posts: 6
    Ahhhh file format not allowed let me convert to avi maybe thatll work
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