Don't ever leave the black tank valves open. Only to dump. Even in camp at full hookup, dump then close until full again. All that liquid helps the solids break down and your drop in pods or liquids to help digest and break down solids and hold down smell.
Leaving the black tank valve open and all the liquid runs out the hose and all the solids pile up... the infamous Poo Pyramid. Get a big wad of toilet paper and soak it good with the outside hose. Set it down and leave it, after a day or two of drying out pick it up. Solid and dry, and usually stuck to whatever it was setting on. Same thing happens to your papers and solids without liquid in the black tank. All that liquid help carry it all down the hose when you dump. I like to dump when the tank over half full, prefer 3/4 full. If a short weekend doesn't net that much in the tank, oh well I use the flush valve to fill it more or dump in some water down the toilet.
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