We like camping for extended stays, so what do you do about the black and gray tanks filling to fast? You buy a portable holding tank! We researched the tanks first and a lot of the reviews talked about the wheels cracking, so we replaced the wheels before we used it. With the original tank you put the hose in the hole and empty but we didn't like that so we added a valve, we don't want to see anything! If you put the correct amount of chemicals in your tank you shouldn't smell anything. We have been around some campers who don't use chemicals...not pleasant! Problem solved, we are now ready to roll!