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Thread: cascading water in pipes

  1. #1

    Default cascading water in pipes

    I read a question posted by uglier on 11/16/04 concerning noisy baseboards after replacing the boiler...and I'd like to know too why this is! I have the same problem in that you hear the water literally cascading thru the pipes at the inital call for heat. As he had done, I too have purged the pipes but to no avail and I even tried to introduce a bit more water into the system only to have the relief valve trip out. Any thoughts on this??

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    A couple of things I can think of (I'm not a pro). It can be a pain depending on the system design to get all of the air out. Does your system have an air purge valve? One brand I'm familiar with is called SpriroVent. This goes inline and sort of 'combs' air bubbles out of the water stream and releases them out of the closed system. You may have something like this and/or one of themore common types. You system should also have an expansion tank. Make sure that it is not full of water. Tap on it, the top should sound hollow, while the bottom, having some water in it, won't. Sometimes, these things are inverted - the side away from the inlet should have air in it. If it is full, it needs to be replaced.

    If you have a good air extraction system, eventually, it should purge all of the air out of the system, and it should quiet down. In the interim, if there are any purge valves at the highest point, try opening them and see if you get any air out of the system. There's probably a purge valve at the boiler, too, try that and see if you get any air out.

    Air in a closed system is not a great thing. the sooner it is purged, the better. Once all of the air is out, opening the valve should be nearly silent.

    My unprofessional opinion...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    Thanks for the reply...I'm no pro myself...the system is yer basic hw baseboard vintage '60's with purge valves at each run of room, I got a few bubbles out two weeks ago...I replaced the old Am. Std. with a Sabre by Hyrdotherm, but not being too familiar with it, I can't say I know of a purge on the unit itself.
    Let me run this by ya...last year I fed a little water into the system, but perhaps I didn't allow enough for expansion and had "popped the top" on the relief valve,so I bled 'er down...right now I'm steady at 16-17 psi's...do ya think I should add about 3, now that it's been a year that the system has been running?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    Does your system have an expansion tank? I think that without one, you are just asking for problems. In between the boiler firing, the contained water contracts as it cools then reexpands when the boiler comes back on. Something has to give. If there is the slightest leak in the system, the vacuum will draw in some air or stress the components. If you get too much pressure upon reheating, the relief valve will let some water out.

    The owner's manual should indicate the operating pressure. What you have is typical from the few I've looked at. In my jurisdiction, a water makeup valve is required - it is a one-way valve that automatically adds water to the system if for some reason the pressure drops. This has good and bad points - if you have a slow leak, it will keep the system full and prevent the boiler from trying to run dry (many other safetys there, so not usually a problem). It also will keep the system full as the other devices purge out air when you first fill the runs.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5

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    Hi again, yeah I have an expansion tank and bell valve, my area require the same...I'll have to check with the Manufacturer about the recommended psi to the system..I guess thats' what I get for letting a freind of a freind do the job instead of doing it myself, thanks again for the thoughts and if ya come up with anything please let me know...I'll keep ya posted on the cituation!

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    These things typically run at about 1 atomosphere - 14-15#.

    Double check your expansion tank - it should sound hollow on the dry side. If it is filled with water, it probably needs to be replaced.

    Try going to the highest radiator in the house and purging air from it again. Some air gets trapped in the water when it is circulated, and only comes out of suspension when it sits for awhile. That is where the SpiroVent works well (there are probably other similar devices). It has what sort of looks like a comb, and air tends to accumulate on it and eventually, it opens a float which allows that accumulated air to escape. Kind of neat. Many of the other type of vents only vent gaseous air, and can't extract it from the water stream.
    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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