\nThe following is according to my understanding.<\/p>\n
\nFor years, when someone would turn off a tap, sometimes one would hear pipes hum elsewhere in the house. The hum didn’t seem to come from a specific place, but was sometimes quite loud. Opening a tap would stop it again. I looked around the Internet, but couldn’t come up with a diagnosis, back then.<\/p>\n
\nThen, another thing happened: as I recall, one of the toilets wouldn’t stop refilling. One of the seals on the fill valve, I supposed, was worn out. Small wonder: said toilet was over 20 years old, and I didn’t recall its fill valve ever being replaced. I went down and bought a universal one.<\/p>\n
\nRemoving the old fill valve, I noticed one of its seals was almost completely gone: only a powdery remnant of it remained. Hence, there was plastic touching plastic, which likely led to vibration that caused the humming.<\/p>\n
The new fill valve was fairly easy to install; perhaps that’s for another post.<\/p>\n
\nAs I recall, once the new fill valve was installed, the humming stopped. It’s been months since I replaced the fill valve; I can’t remember the last time I heard pipes hum.<\/p>\n