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Won't Purge....Why?!!!!!!

Rich Member Posts: 20
I have a H.W. closed loop heating system that every two years or so needs to be purged.You can hear the noise of the air every time the circ turns on. For the past ten years I have had to purge this system. My records show that this has been happening almost every 24 months.I would purge and have no complaints until......! How is the air getting into the system. cannot find any leaks. Have changed the auto vents on the top of the boiler and the top of the air scoop.Purge, Purge ,Purge. Still, air. Replaced the air scoop with a one inch spirovent and the system quited down dramaticly.But I am sure the air is still getting in. Is there anything left to check? How does this air infilltrate the heating system?


  • Have you read \"Pumping Away\"

    by Dan Holohan? That would explain it clearly....
  • Air is usually introduced

    into the system with makeup water . With the spirovent on the boiler , I'm assuming theres a bladder expansion tank ? And how high from the boiler is the highest loop of heat ? We had a problem job once that kept getting air bound - we wound up installing a water meter on the feed line and saw it was actually making up water . Turns out there was a 3/4 copper pipe running into a slab to go to baseboard - but it only leaked when the pipe was cold . Good luck .
  • Rich
    Rich Member Posts: 20
    Pumping Away.

    Yes. I read pumping away years ago. Was taught about it before the book was even published. Any ideas on how this air is getting in?
  • Dale W.
    Dale W. Member Posts: 42
    Need more info

    Is this a one story or multi story house?
    What pressure are you running? Where is the circulator?
    What type of expansion tank?
    This should give us a fairly good start.

    Dale W.
  • Rich
    Rich Member Posts: 20
    NO slab!

    Thank you. You may have touched on something about the pipes getting cold. After a long period of time, the temp changes could be causing this so called leak. I'm sure make-up water is the culprit.But what do you think is causing the auto feed to fill.No slab exists but, after a 24 month period temp changes could be the poblem. Any other thoughts would be appreciated. Thanks Rich..
  • Rich
    Rich Member Posts: 20
    Dale - more info...

    Utica star fire three boiler. Taco 007 circ. Three taco 3/4 inch zone valves.Amtrol mod.30 extrol tank. Watts 1156 PRV. Watts 9D BFP. Spirovent air scrubber. Heating a 2600 sq. ft. two story dutch colonial. 12 psi is the pressure. O.K. the circ is on the return. But hey! Plenty of systems are installed this way and don't do this.The boiler has a tankless coil. Is the gasket on the coil sucking in air? Could the auto vent on the top of the boiler be sucking in air? Hope this new info will will be helpfull. Thanks Rich.......
  • This sounds like a stupid question

    But when you purge , do you jack up the pressure ? We try to keep it around 20 to 25 psi. when purging .
  • Rick Kelly
    Rick Kelly Member Posts: 40
    Air in system

    Shutoff your makeup water, note your system pressure, and confirm whether or not you have a leak. If it has taken so long between purgings to notice air infiltration, that new Spirovent is going to make it impossible to detect any new air.
  • Gary
    Gary Member Posts: 29
    Book , Pumping Away

    Where can I get a copy of " Pumping Away"
  • Steve Ebels
    Steve Ebels Member Posts: 904
    Check out

    books and more on the left of the screen. Click on it. It'll open a whole new world for you.
  • Roger_3
    Roger_3 Member Posts: 4
    Fix it for good

    You can replace the Feeder,Expansion tank and Gauge(making sure you really have 12-15 psi on system) make sure the tank has 15 psi in it, or fix it right and put the pump on the supply you may never deal with it again.

    Happy Heating
  • Rich
    Rich Member Posts: 20
    jack up the PSI.

    Yes I do jack up the pressure. When purging ,Im always use the "fast-feed".
  • Gary Usa_2
    Gary Usa_2 Member Posts: 45
    silly question

    hiya .may i ask how are you purging the system.where are the purging valves installed and the isolating valves positioned.just trying to help you.have you got base board are all the vents etc ok have you pressurised the sytem and isolated sections of it yet.

    hope this may give you room for thought

    all the best

    gary usa
  • Dale W.
    Dale W. Member Posts: 42
    Tank Location?


    Where is the expansion tank?

    If you read in your Pumping Away book you will see how important it is to install the circulator after the tank.
    This make the lowest pressure point at or near the Spirovent.

    Placing the tank after the circulator will make the lowest pressure point somewhere on the second floor. This is where the air will come out of the water. Each time you purge the system you put in more air laden water. The purging removes the air from the last batch of water, but it's only a matter of time before the air comes out of the new water and goes somewhere. It sounds like your somewhere is second floor.

    Hope this helps.

    Dale W.
  • Terry
    Terry Member Posts: 186
    circ on return side?

    circ is probably sucking air in thru pump seal or auto air vent located near the pumps suction side.
  • Air in a closed loop system

    If you only have to purge the air out of the system every two years, you are very lucky. The only way air enters the system is that you have a minute leak and air is sucked into the system or the makeup water is adding air into the system. Any water feed that introduces water into the system, also adds air into it. Nothing is perfect in an imperfect world.
  • John_54
    John_54 Member Posts: 17
    Blocked pipes??

    I'm using 2 gas boilers and convectors to heat a 50 year old, 4 story, 24 unit building.
    I have 2 heaters that won't work. One on the forth floor and one on the 3rd. The heat everywhere else is good. I can bleed water out until it gets hot but either the supply or return pipe is obstructed and the heater gets cold again. One of the blocked convectors has a pressure guage on it and the pressure is about 25lbs on the forth floor the system pressure is set at 35lbs. Is there a safe additive I can put in the system to clear the pipes. I don't want to create any leaks. The water is clear when I bleed the rads.
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