I'm ok with running both. What I thought was a bad idea was re-routing his city water connection into his freshwater tank.
Maybe he just FILLED the FW tank from city water. If you have the anti-freeze connection, you can hook your city water hose to that, then open the valve to the pump and back fill your FW tank. You need to be careful and not over-pressurize your FW tank. Make sure you have adequate venting available. He can probably do this once a day. Then he just runs his normal pump from the FW tank. Only issue I really see is wear and tear on the pump.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10