Bring up this question online and you’ll get lots of different opinions. Why does it really matter?

Well, it matters because you want a lot of liquid in your tank before dumping to help flush all the solids out. If you dump your black tank on a daily basis, or worse, just leave the black tank valve open, you’ll get the dreaded poop pyramid. All the liquids will drain out and leave the solids. The goal here is to make sure your black tank is over half full before dumping, which takes us back to the original question – when is it really full?

Tank sensors are inaccurate, at least after the first couple of uses. Some people use a set number of days. That might work – after you’ve figured it out some other way but tanks are different sizes and the way people use their toilets is infinitely variable. Some folks just get a feel for it, but verify by shining a flashlight down the toilet pipe. I guess that works but, ewwwww!

I personally wait until my toilet burps back at me. What????? Yes, when you flush your toilet and the tank is full enough to start covering the vent pipe, it will burp at you. You want to pay attention to this when it first starts burping. You really don’t want that to happen after taco Tuesday, if you get my drift. Some folks just can’t visualize a burping toilet so I made a video of it for your viewing pleasure. Feel free to rewind or use slo-mo.