Towing with half a tank

I agree with the above... either 100% full or 100% empty. A full tank has no room to slosh. A partial tank will always have shifting water (like at an ocean beach), waves in the tank beating around. If 100% full, there's nothing to "slosh".

Now, your black tank? If you want a good cleaning? Fill it 1/2 full and go for a drive! it will beat everything loose.

We travel with at least 1/3 tank all the time......great for roadside stops and is enough just in case.

At one time DH worked for a company that hauled water and also knew how the military hauled water. His believe is you travel full or empty. I can't explain it - Sorry.

Sort of depends on WHERE your tank is located.

If the tank is FORWARD of the axles then you may not have enough tongue weight when partly empty. If tank is on or behind the axles towing with a full tank or partial tank may be adding too much weight behind the wheels basically reducing tongue weight.

In any case, one must remember that these tanks DO NOT have "baffles" in them so when towing with a half full tank you WILL experience sloshing effect from the water in the tank.

This can be substantial in your case especially with 50 gallons moving around in a 70 gallon tank. You will have about 400 lbs of water slamming back and forth, this would feel like hitting three big deer at the same time over and over again.

It is for that reason as to why you should either fully fill the tank or only put a few gallon in it. A full tank will not have much if any room for the water to move so it cancels out any potential slamming effect.

I would recommend filling it full and not worry about the extra 20 gallon you don't use..