City Water & Fresh Holding Tank - 2017 Outlaw 29H C Class

[Kickstand]

I never use city water. I’ve been happily running off holding tank since I got the coach for nearly two years. No problems. Recently I was glamping for 10 days with full hookup. I read the manual and didn’t see any special steps to use city- just to turn the pump off and make sure city pressure was below 55psi. I did that, and CG pressure was only 35psi, but kept my pressure gauge on anyway, still set at 55. Everything worked, but I noticed water in my holding tank just above the first level sensor. I had just sanitized my tank and system a month ago and *thought* I had emptied it completely, but maybe I missed that final 1/4 tank. Not wanting any water in there, I went ahead and drained it. Then a couple days later I’m cleaning out the pump screen and notice it’s right back to the same level. Is there some diverted I was supposed to twist when switching from holding to city? There’s a pex hose with a diverter on it and a small pigtail with a hose connector above that’s between pump and tank, but I thought that was for sucking up antifreeze or compressed air for winterizing. Wouldn’t the pump prevent back flow? I had a pic but deleted it by mistake.