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Clicking sound from the Taco air scoop

agn Member Posts: 6

I have a hot water baseboard heating system. When the circulator for one of the zones starts, sometimes, a constant clicking sound (roughly 350 clicks a minute) seems to come from the Taco air scoop. I've tried looking at the baseboard pipes to see if the pipes are touching something as the hot water flows through them but it looks to me like it is coming from inside the Taco air scoop.

This doesn't happen every time but it happens often enough that it is very annoying. Also, couple of times I happened to tap the water vent above the air scoop and a burst of air/steam came out of it which instantly stopped the sound. Other times, I've tried tapping the vent and nothing happened. The water vent is a vent-rite 700F.

Any idea what's causing this sound? I'm attaching a photo of the air scoop and the water vent.

Thanks in advance.



  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,665

    I am not a professional, but I do know that steam should not come out of that vent because there should be no steam in the system. It must be running way too hot. Usually in a home heating system, 180F is the maximum it should run at. Perhaps the clicking sound is the water cavitating or boiling in the air scoop.

    (There is something funny about your picture. The vent at the top left of the scoop is to let air escape from your system. Yet the pipe at the top right of the scoop is normally there to let air removed from the system get back into a conventional expansion tank. Which do you have? If  conventional tank, that air vent will help the tank get water logged, which you do not want to happen. If a diaphragm tank, the pipe at the top right of the scoop should not be connected.)

    Also, you should not have to tap the vent to get it to release the air that can collect inside it. If it is like mine, a float inside just drops to open the valve there. If the pressure in there is too high, perhaps that holds the valve closed.

    Better have the boiler temperature and upper temperature limit checked, and be absolutely sure your pressure relief valve is working. You may need a professional to check this out. It could be a matter of life safety.
  • Ron Jr._3
    Ron Jr._3 Member Posts: 603
    Right on

    about the air vent . If the 3/4 pipe is connected to a compression tank , you don't want or need that air vent there . It'll waterlog your tank pretty quick .

    The clicking noise is probably air passing the flow check to the left of the air scoop . It'll rattle the weighted check until it passes through . Try bleeding all the zones thoroughly and then drain the tank , if its a compression style .  
  • agn
    agn Member Posts: 6
    Expansion tank

    Thanks JDB and Ron.

    That pipe on the right side of the taco air scoop is going to an expansion tank. I've attached another picture of it. You can see the air scoop on the left this time and the pipe coming out and across to the tank on the right.

    So it looks like there is both an air vent and an expansion tank.

    The boiler is heating the water to 160-170 degrees at 12psi.

    I opened the expansion tank's drain faucet just a little and some warm (not hot) water started to trickle out. It could be that the expansion tank is full already. I'm not sure how I can confirm that.

    Also, I wanted to mention that the clicking sound comes on as soon as the circulator pump comes on, and before the boiler fires. When the boiler turns off, the sound continues as long as the circulator is going. The sound stop immediately when the circulator stops. I think this is in line with Ron's suspicion about the flow check.

    Is bleeding the system a complicated process? Since I'm not too handy with this, I'm considering bringing in a professional to bleed the system and the expansion tank.
  • billtwocase
    billtwocase Member Posts: 2,385
    my guess

    is the flow check before your air scoop is the culprit. 
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,665
    Looking like time for a professional.

    If it were up to me (luckally it is not), I would replace the tank you have with a diaphragm type of the proper size. It is probably easier to abandon the one that is there now and put the new tank somewhere else (lower). If you insist on keeping that tank, you will need some fittings that you may not have, and the connection to the tank still have to go uphill all the time so the air from the scoop will percolate into the tank. A pain between the back pockets. In that case, you would still have to replace the air vent with a solid plug.

    If the temperatures of your system are as you say, and if steam comes out even when you have just started the boiler, I am completely mystified. I recommend a pro to get to the bottom of this.

    Bleeding the system is quite easy if all the necessary valves, vents, or both, are in the proper places. My guess is that they are not. If there is only a slight amount of air in the system, the air scoop might get them out in a week or so.
  • agn
    agn Member Posts: 6

    Thanks all - I appreciate the information.
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