I installed a timer on one of my outside faucets a year ago to water my plants several times a week. Recently it has caused the water pipes somewhere in my house to hum. The only way to stop the humming is to turn the water off. Any ideas why it just started and what I can do about it? Thanks

Check to see that the timer is turning the valve off completely. It may be hanging open just enough to to allow some water through, creating turbulance in the valve which could be causing a vibration that you notice as a hum.