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.

Loud noise and small leak from furnace

CloudM Member Posts: 2

I came home after being away for a few days and turned the temperature back up in the house. After the furnace was running for a bit (about 15 minutes maybe) I heard a loud noise come from the basement and went down to find water came out from under the furnace. It wasn't very much, maybe a half gallon or so. It has stopped leaking after that initial amount. While I wait for the service provider to call back with a time to schedule an appointment, is there anything I need to do? Turn off the power, turn off the water, etc.

Thanks in advance.


  • Weezbo
    Weezbo Member Posts: 6,232
    i do not know how timely this is ...

    however , you could go look at the temp pressure gauge ... i think there is some chance that was the boiler relief.... you could manually open a zone ,and see if there is any pressure change , with the power off , then do that with each and every other zone valve...

    if something changes drastic like the pressure drops right off then that might be a sign that zone has some problems ..

    point that out to the guy who comes over to help.


  • CloudM
    CloudM Member Posts: 2

    Thanks. I was able to talk to the contractor and she didn't think it was enough of an issue to need to shut it off completely. She walked me through adding water to add pressure (it was only at 8psi) to get it up to 15psi. No more water leaked then and nothing out of the ordinary happened when I turned up the temp to get the system to run. Hopefully it was just that it was low on water. Still having her come in tomorrow to check things out just in case there is something more serious.
  • icesailor
    icesailor Member Posts: 7,265
    I went away. And then I came home.

    More likely, you went away and turned off your boiler so it wouldn't use any fuel. Because it is a cold start (it only runs when it gets a call for heat) and not a "warm Start" where it maintains some boiler temperature, the water all shrunk to its lowest level in the cold house. While you were away, the system pressure dropped and the fill valve added water. Now, the closed heating system has too much water in it. When you came home and turned on the cold system, the boiler started to heat the water that expanded and blew the relief valve.

    If the boiler is a blue Weil-McLain *68 Series, and it gets cold, it will leak like an old rowboat until it gets hot. Some other boilers do it just as badly like Peerless JO/JOT's.

    Next time, don't shut your heat off. Set your thermostats to 40 degrees. It's cheaper than the service call you will pay to have someone come and look for something that they won't be able to find. Unless you called me. But you wouldn't believe what I am telling you.