How often should you dump your black water tank?

The short answer? When it needs to be dumped!

When you decide to dump your tanks depends on when they are full. Normally, this is determined by looking at the tank sensor monitors inside your RV to see how full they are. A lot of tank sensors don’t work (because of that tank solution you’re putting in there), so most RVers with this problem develop a sense of when their tanks are full (or nearly full).

The long and short of it is, you want to empty your tanks — both black and gray – before they start to back up. Here are a couple of things to consider:

First, it’s important to realize that your holding tanks are not a septic system. They merely hold waste – either black (toilet) or gray (everything else) water – until you are ready to empty them. There is no need to add enzymes, chemicals, or biological agents into your tanks to dissolve solids. Doing so, in fact, especially in your black tank, turns the tank’s contents into a thick, sticky, pancake batter-like slurry that is virtually impossible to completely get out without a professional tank cleaning.

Next, if it’s possible, empty your tanks when they are 75% to 100% full. Why? Emptying a full (or nearly full) holding tank creates a whirlpool or vortex due to the pressure and weight of the water in the tank. This vortex pulls waste from the corners of the tank, resulting in a more thorough flush. When you empty tanks that are not nearly full, the liquid tends to seep out slowly without fully flushing the tanks clean.

Finally, you may think that you should pull your black tank’s gate release valve first, then the gray’s. Actually, the correct order is: gray (count to three), black (to empty that tank completely), gray (to empty that one completely and flush out your waste pipes and sewer hose). Why? A dry surface (like your sewer hose) will “hold” on strongly to whatever liquid contacts it first. By pulling your gray release valve first and counting to three, you “coat” the inside of your sewer hose with cleaner water. And since that’s mainly soap, anything after (like your black tank’s contents) will empty faster and more thoroughly.