Tom, check out https://www.askmehelpdesk.com/showthread.php?t=14182

Sorry Labman,

While we install and pipe , ice makers, disposals. Water softeners,pumps and septic systems in my area service and repair are separate trades on these items. Tom

I was hoping you would know how air gets in any water line and how to stop it. Could water passing the line tap draw water out of the line and draw air in through a leaky valve?

Could water passing the line tap draw water out of the line and draw air in through a leaky valve?

Stop and think Lab, Since the water's under pressure a leaky valve would squirt water out , not draw air in.

This could only happen if the water drained out of the filter cartridge some how letting air into the supply line. Not very likely! More then likely you'll find it in the internal workings of a solenoid valve or timer. Regards, Tom