I have left a message with a recommended heating repair company, but while I’m waiting, please assuage my concerns.
We have a hydronic (hot water in the floors) heating system combined with an on-demand hot water heater that is about 8 years old. Yesterday it started making this continuous high-pitched tone; sometimes the tone varies a bit in pitch or intensity, but it’s pretty steady. It goes away for a while if I turn the system off and when I turn the system back on it takes a while to come back (I don’t know how long, at least an hour).
The backflow valve is inspected every year by city ordinance; other than that, it has had no attention since being installed.
My question is: is this noise a prelude to explosion or other disaster, or can I leave the system on until I hear from the heating company?