Dont know. Are you sure you had all the valves turned right? What were you sanitizing? The black tank or the fresh water tank? Did you have a place where air was getting in the water system? That will make water flow real slow.
The low point drain is not unusual (on the 31FK). I see drains located there everyday. inconvienent YES, unusual location NO.
I started with nothing, and still have most of it left
2001 Jayco KIWI 23B
2003 Jeep Grand Cherokee 4.7 AWD