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loud shaking / vibration around thermostatic mixing valve pipes

shrujanm Member Posts: 4
edited January 2021 in Gas Heating
Hi All,

Exhausted all the resources online - so posting here as last resort. Kindly help.

I have weil mclain tankless gas boiler. The issue is when i hear sudden shaking of pipes around thermostatic mixing valve (Honeywell AM-1 series) - the shaking is so loud that I can hear it across all the floors - it continues for a while then stops on its own. I couldn't tie this back to hot or cold water consumption as it even starts in middle of the night. It happens when flame is on or off.

The shaking stops immideately when I shut off the cold water going towards boiler and mixing valve. So just want to know - what might be the issue.

reading from boiler dial
- Pressure - 20 psi
- Water temp in boiler - 140 F
- H2O - 70 feet


  • Larry Weingarten
    Larry Weingarten Member Posts: 2,782
    Hello @shrujanm , Is it possible for you to post pictures, both close up and from a distance of the valve and associated piping? I'm thinking that will help in troubleshooting.

    Yours, Larry
  • hot_rod
    hot_rod Member Posts: 18,190
    A mix valve on the boiler, or is it on the domestic water,
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • shrujanm
    shrujanm Member Posts: 4
    Thank Larry! Here you go.

  • shrujanm
    shrujanm Member Posts: 4
    in 5th pic, you can see the cold water valve on the top right corner - if I shut that down, the vibration stops immediately.
  • shrujanm
    shrujanm Member Posts: 4
    @hot_rod mixing valve is taking hot water from boiler and cold from mains and then send it out to domestic use. let me know if I answered your question.
    EBEBRATT-Ed Member Posts: 13,097
    The valve looks like it's piped ok except a pressure relief valve is usually put on a tankless heater and I am not sure if that valve needs to be trapped.

    What is the history? That valve looks like it's been there a while. Did it just start acting up? Or has there always been issues with it?

    If It just started I would replace or rebuild the valve