You say you can hear water cycling....but your water pump is turned off...so you just hear water flowing? Not the actual water pump? You say you connected to city water...are you still connected? If so, and your pump is off as it should be if connected to city water, and you hear water flowing, then it has to be coming out somewhere. Do you have one of the onboard water filters? If so, check it asap, as it may be leaking in your trailer. Are you sure all taps are off, including outside shower if you have one. The amount of water in your holding tank is irrelevant if your water pump is shut off.
2011 GMC Sierra 2500HD
2014 Rockwood 8289WS, Diamond Pkg.