Our radiant heat boiler tends to "flush" very loudly every night. It seems to go on for awhile too. We have three zones and I think it just happens with the one zone in our bedroom. From my understanding, this may be caused by low pressure. First, could this be a cause of this flushing or running sound in the radiators? If so, what should the pressure be or does this vary? According to our gauge the pressure is at about 25psi.
I would like to get some idea of what the issue could be before we call in someone to look at it and fix the problem. Thanks.
Best Answer
Air trapped in the lines. There is usually an automatic air vent in the system but not always. It should be mounted to an "air scoop" or air separator which may also connect the expansion tank. Though that setup can vary. One name brand air vent is the Hy-Vent. If you don't have one, you should have one installed. If you are handy, install it yourself.
And this could be a sign of bigger problems as air doesn't magically appear in a hot water system. Have you noticed any water on/near the boiler? Your expansion tank diaphragm could have failed and air has leaked into your lines. You can test that with with a tire gauge as the fitting is the same as a car tire and is under a cap on the opposite end of the pipe. CAUTION! Let the system cool down a bit before you do this otherwise you might get sprayed with scalding water.
Another thing to check for is leaks around the baseboards and piping. That could be admitting air into the system.