Solid waste is not nearly as problematic for your plumbing
as the liquid waste is, but of course you want to get the lines cleared out and you don't want any kind of waste to stand in the pipes. If you're pumping into a holding tank
, however, you will be balancing the question of your tank capacity.
Do you know how much you have to pump to completely clear the lines? Neither do I. But I always pump straight out (tidal waters), so I pump a lot to be sure, and don't worry about any tank capacity. If I were pumping into a tank, I would figure out how much is exactly the right amount of pumping. Full holding tanks
are a PITA.
or fresh doesn't matter with solid waste. With liquid -- fresh water doesn't react and is better.