Chances are it's water causing the valve to vibrate as it flows around the stopper. Sometimes there's just enough pressure to overcome the spring but not push the valve stem all the way to the end of travel. When that happens, it'll "sing to you" when the flow rate is just right.
She might want to try a regulator on her city water faucet, or if she has one, adjust the pressure up a couple pounds. Chances are it'll stop "singing" at the next campground, so no real need to change it out. If, later on, it doesn't stop, then a replacement if it bothers her. But, as you advised, if it's not leaking, there's no danger of damage to the trailer.
__________________
John
2015 F250 6.7l 4x4
2014 Cougar X Lite 27RKS
|