No. You must have a volume of black and gray water to flush the tanks out properly. Leave them closed until they are nearly full, then dump, black first, then the grays. If you have a black tank washer use it. Flush the gray tanks with running water. Finally, fill the black and gray tanks with a few gallons of water to keep the seals from drying out and any remaining sludge from hardening. If you don't know about the geo method for cleaning, here is a link: https://sites.google.com/site/cbruni/
Even though you do not travel with the camper often, the geo method will help keep the tanks clean.