I don't put any anti-freeze in my fresh tank, and only a couple cups (using each drain) in each of the waste tanks since the waste lines can't be blown out like the fresh lines. My trailer has two kitchens and it takes about 1/2-gallon overall each time I winterize (again, blowing out the entire fresh water system).
I've always tried to avoid that in my own boats (and RV's) and also the same at the boatyard. Reason is that even the pink, non-toxic anti-freeze leaves an aftertaste and foams *forever* when it comes time to use the tank again. And the tank itself shouldn't have a problem as there is tons of expansion space if it's been drained.
We'd usually blow out lines and drain the pump, then add a small amount of anti-freeze (or Vodka in not-very-cold climates) in case there is any water in low points. No anti-freeze in the tank.
Also, drain and bypass the water heater vs. putting any anti-freeze in it, if you have one.
I wouldn't use antifreeze. Just use compressed air and blow the lines out and empty the tank. If you want to prevent growth in the tank, add some alcohol (>1%) to kill most anything that will grow in the dark.
SOLD04 EB350 Custom Floorplan
6.0 PSD 4.10 Posi
Salem Kroger coil spring 4wd
SMB Trailer w/AT Air Suspension
Alaska to Key West, Labrador and more
130685 miles 16.65 mpg average
Prostate cancer survivor. viewtopic.php?f=8&t=11099
2015 VW GTI
Leaving CA for WA