Re: How big a holding tank vs. camping
Been doing this near on 35y and have been pooping longer than that. Boats can have boat smell but never poop smell. Poop smell means something is wrong. May be as simple as clogged vent line or as bad as need for a rebuild. Knock on wood never had a failed leaking holding tank. Right now need to shorten sani pipe from head discharge to holding tank as it's too long giving a small amount of back flow. Once done no reason for smell. On prior boats have had to add enzyme but now with fresh H2O flush additives not needed. If you have smell or are needing to add things constantly may want some advise as to what's going on. Could be the piping- common with old boats or production boats the best piping was not used.
Also found the tea tree stuff really works to get rid of boat smell. That and good ventilation with a full wash down of all surfaces with vinegar once a blue moon.