That smell in your RV? It may not be your black holding tank.

“My gray tanks aren’t dirty!” We hear it ALL. THE. TIME. But you might be surprised to learn that your gray holding tanks can be just as dirty as your black tank — and in many cases, even dirtier.

We’ve worked on close to 1,000 holding tanks over the last six years and we’ve seen all kinds of situations, both good and bad. We all expect our RV’s black tanks to be dirty — we know what goes in them. But we’ve seen just as many gray tanks that made our stomach’s turn.

Here are some photos from a recent job. The customer’s black tank was actually pretty clean (compared to a lot of them), but the gray tank had a thick sludge in it with “chunks” of stuff. That stuff — once we filtered them out of the sewer pipe — ended up being a moldy slime.


“Mold in my holding tank?!” Indeed. Most gray tanks (and black, for that matter) have mold in them.

Your holding tanks are moist, hot, and full of natural yeast, bacteria, and other biologicals. The perfect situation for mold to grow and flourish.

So the next time your RV has “that smell,” it’s highly likely it’s your gray tanks as much as your black tanks. All the more reason to have our service and get your holding tanks professionally cleaned. We’ll even teach you how to keep them that way! Call or contact us today for more information or to get a free quote.