While troubleshooting my back-up (backup) valve I was finding inconsistent info as to how much water should be coming out while the valve is closed. Below is a link to 2 videos: one shows the 14 year old valve and the other shows the new "Polaris" branded valve, which has just a trickle when closed. I was told by Polaris that some leakage was normal. I had tried flushing out the old valve but that did not help.
Back-up Valve video before and after
Back-up Valve video before and after