DJC
with the 31QBS the pump is on top of tank and pump sucks it up. Raising tongue won't do any good
.
the suction tube for fresh water is on side of tank, but not at the bottom.
Some water is always in tank. and can not suck it all out.
you need to ,under seat by entrance door, turn vavles and suck antifreeze from the hose by pump.
unless you put 5-6 jugs antifreeze in FWT to delute the water. And then it may not be strong enought strenght wise.
AND BEFORE YOU USE FRESH WATER TANK, YOU WOULD HAVE FRUSH AND FILL LOTS OF TIMES.
When I first got my unit. I wanted to flush fresh tank. I HAD water running for 6 -7 imutes at a good flow. nothing was coming out of drain line. I panicked thinking the lines was disconnected and flooding my under belly.
Finally it started to flow out drain.
NOW UPON DRAINING TANK. when pump quit sucking water I still had water showing on tank level. when I was driving home and parked trailer on unlevel , sideways, water started to pour out of FRW drain.
went across city and again parked on other side of road and water started to pour out again.
BOttom line. you don't get everything out of tank you put in. so Don't pour antifreeze into tank unless you want to spend a lot of time trying to get it out later