Thanks for your question and thanks for your service from a SandyHobo. Our nation service is marketed as a "full RV flush" which includes black/gray/waterheater. That price is $200-250 and takes 2hrs. to complete. Just a black or gray tank is:(B-$125 / G-$100) We also service the waterheater $75 / new anoide rod.
HERE's a funny story...........I did a seminar at the 50th Anniversary FMCA Rally in Gillette, WY. I had 250 people at the gathering and I told the "ice cubes in the tank trick" after I was finished one man raised his hand and said, "after I stir my tank with the ice....................(Wait For It) how do I get the ice out of my tank??