Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Filling Steam Boiler makes Hot Water tank gurgle

So this is weird. I was cleaning my Boiler and when it was time to fill it back up, the gas hot water tank beside me started to gurgle. I thought it was sucking from the tank so I shut the valve bringing cold water into the hot water tank and it still did it. I shut the hot water so they were both shut and it stopped?
Also after adding water to the boiler, how long should I run it to burn off minerals etc?


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,852
    edited October 2022
    When you open the valve to fill the boiler, the water pressure in the DHW tank will drop. This noise is normal. Sometimes there are metal parts of the water heater that are hotter than the water in the tank. If you lower the water pressure, those hotter parts will allow some of the air that is dissolved in the tank, to flash-off some micro bubbles. If enough micro bubbles join together, they become a larger bubble that is more buoyant and will crash into other sections of the tank and give up a harmless noise, like air bubbles sometimes do.

    Oddly enough, the same thing happens when you open the tap to fill the tub or a garden hose to water the flowers or fill a bucket. But like the tree falling in the forrest, when no one is there to hear it... you are too far away to notice.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?