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Thread: Taco Check Valve Chatter

  1. #1
    DIY Junior Member house5's Avatar
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    Default Taco Check Valve Chatter

    I have been hearing a clearly audible chattering in my hydronic heating system since a new boiler was professionally installed two years ago. The circulators, tubing and all valves associated with the boiler were installed at that time. The noise now seems to be louder - anyway, it is getting on my nerves. The noise sounds like it is coming from a Taco 241 Swet-Chek valve. The system has three zones (two house and one indirect hot water). Only one of the check valves is making noise. The one that makes noise is on a 1" house zone line that comes off the main line through a T but almost immediately takes a 90 degree turn through an elbow just before (3") the check valve. The other two zones are 3/4" lines, don't have any elbow before their check valves and don't make noise. While the tube size difference might suggest the cause of the noise is constriction or insufficient flow in the 1" line, I doubt it because I quickly get lots of heat in that zone. I think that the problem is turbulence from that 1" elbow causing the check valve to flutter violently. If so, the answer would likely be to move the check valve a couple of feet beyond any elbows. Any other thoughts about more likely causes and solutions? Thanks!

  2. #2
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    What make zone valves do you have? Some zone valves don't require you to have a flow check in the line.

    John

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    In the Trades Tom Sawyer's Avatar
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    Rattling flow checks are usually caused by air in the system.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    DIY Junior Member Joe Steam's Avatar
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    Default Low Flow

    If not air, check valve will chatter if the flow through them is too low. Could something have changed so that the flow decreased in this zone? Maybe you can put in a 3/4" check valve and this may help.

  5. #5
    DIY Junior Member house5's Avatar
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    Default Swetchek noise

    Thanks, guys, for your comments. Sorry about the delay in responding, I've been real busy. First, I have figured out that if I raise the valve plate with the thumb screw, it stops making the rattling noise. I think the turbulence idea is still a contender here; Taco says it should be 16 in. from an upstream ell, I have read elsewhere on the web. Moving it (and the gate valve downstream of it) would take some work. It would be nice to try to eliminate other possibilities first.

    Let me take your comments in order. First, John, there are no zone valves. There are three Taco circulators. They were new in 2010, there is one for each zone, they are mounted on the returns.

    Joe, it is conceivable that the flow on one pump has changed. Supporting that idea is the fact that there is a 3/4" Taco 219 making no noise at all right next to the 1" that rattles. An explanation for that might be the flow from the pump going to the noisy swetchek isn't high enough anymore. I guess replacing the pump guts would be one possible solution, but a bit pricey as a first test. A Taco tech says it is extremely unlikely to be the circulator pump, in any case. I wouldn't want to constrict the flow, so changing it out for a 3/4" isn't an ideal solution, assuming it is flow. Further thoughts?

    As for the air theory, Tom, Taco says that is the most likely. I wonder about it, however, because you'd think the 3/4" swetchek next to the noisy one would also make noise if it was air, or the one off to the side on the leg going to indirect hot water. Just for the record, the system never vents water as far as I know and the pressure is always 15 lbs when I check it. And where would air be entering the system, anyway? Have to be someplace where the 15 lb. pressure wouldn't be pushing the water out, wouldn't it?. The air tank (diaphragm-type) has 15 lbs. of air in it - I checked. Where else could it be? Air vent on scoop? How do you check that?

    Thanks again!
    Last edited by house5; 02-12-2013 at 02:21 PM.

  6. #6
    In the Trades Tom Sawyer's Avatar
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    It's air, believe me and getting it out might be simple or not depending on how it's all piped. Post a picture.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    DIY Junior Member house5's Avatar
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    Tom, your certainty caused me to give the air issue more thought. Early this AM I remembered something. Before I got the Buderus in 2010, the system would from time to time lose pressure and develop that sound of water running through the pipes. I'd open the valve and add water. In retrospect, that was an alarm going off but I wasn't bright enough to understand it, wasn't it?

    If air is getting in somewhere, water is getting out somewhere. As a first test, I put a few drops into the top of the Hy-vent exhaust tube as the only likely candidate for air intake. The water disappeared in an hour. That likely means that air is being sucked into the system through the vent by a vacuum. If true, then water is certainly exiting somewhere. Now that I think about it, it wouldn't create a wet spot in ceilings etc - it would be a pinhole and the water would evaporate, leaving mineral deposit. To test if water is exiting, I'm now going to close the automatic intake valve line and watch the pressure gauge for a few days. If it drops, I guess I examine all visible pipes carefully and, if I have to do so, tear the place apart?

    I am having trouble posting a picture of the piping over the boiler (which I've been told by techs looks good). If you still want to see it, I'll try again later.

    Thanks for your help!

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    An autofill valve can often mask a small leak. Leaks in a hydronic system are bad for more than one reason. Some are:
    - fresh water contains minerals, oxygen, and potentially some organic (probably dead) material
    - oxygen will react with the metals in the system. Once all is 'used up', things are pretty stable, until then, things are 'rusting' or oxidizing
    - a big enough leak could keep things wet and promote rot

    You may never notice a really slow leak. As opposed to potable water, after sitting in a boiler loop for awhile, the water may have deposited most of them on various internal surfaces, and there may not be many in suspension or disolved to leave a trace upon exiting.
    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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