Black water holding tank question

[cufishin]

I noticed that when I dump my sewer there is still liquid in the bottom. I can see it by shining a flashlight in the toilet. How do I get it to dump all the way? I am only concerned because winter is approaching and I want the tank to be safe to freeze. Any suggestions would be helpful.

[Lincolnboy2]

Use some fulltimer's antifreeze.....

Super Tech RV & Marine Antifreeze - Walmart.com

[kb1flr]

A little bit of liquid should not be a problem, but I always add some RV antifreeze to each tank.

Rick

[Shadowcatche]

With a small amount yes it will freeze but if there is not enough to push against the sides when it expands during that process it is not a problem, same with the fresh water tank.

[Superslif]

I wouldn't worry about your gray or black tanks. If you emptied your tanks, at most you might have a gallon or two of "stuff" still remaining. As long as there is a place for the "stuff" to expand when it turns to ice, your fine.

Remember your toilet, to run some RV antifreeze thru it. The shower hose I disconnect from the faucet. I take the inlet fitting off the water pump and attach a 2' (3/4" dia.) hose it and stick the other end into the jug of RV antifreeze. As I hold it, the DW runs each water outlet till pink comes out. I'll also splash a dab of RV antifreeze down each "P" trap just for safe measure.