sounds like somebody's got an education coming up!

with a cassette toilet, you can take out the cassette, roll it down the sidewalk to someplace with a conventional bathroom, and dump the cassette into the conventional bathroom's toilet; then flush. then you walk back to the rv. some people have tote bags for their cassettes to keep this subtle. this is needed a few times a month

blackwater tanks last a great deal longer, months, but at that point yeah you need to go somewhere with an rv dump station. better get the engine running by then. this is one reason blackwater-tank rvs are practically unknown many places

with a composting toilet, your dried poop and composting medium is just another trash bag to take out, about once or twice a week. if you've never used one, you'd assume it stinks, but generally it doesn't. (pee goes in a separate bottle, which you need to empty every day or two.) logistically this is a little bit more work (you have to get the composting medium from somewhere, and if you gather it in the forest, you need to make sure it isn't going to hatch ten thousand crickets to greet you the next time you have to poop) but it's a great deal less risky than having a bottle of raw sewage

And what proportion of the RVs squatting in Seattle neighborhoods do you think have those systems?

Where do you think those squatters are going to dump that waste?

My question stands, why would someone expect a different outcome from the actual one?

i'm surprised to see someone call on-street parking 'squatting'. squatting is an infringement of private property rights (whether or not justified). i haven't lived in the usa for a long time, but from videos i see on youtube, on-street parking seems to be a nearly universal practice among motor vehicle owners, rather than being considered any infringement on property rights, which sounds like an extremist view similar to those of the 'sovereign citizen' movement

i haven't been in seattle this millennium, so i can't do more than guess what the mix is. over 95% of factory-built rvs in the usa have one or another of those systems, and something like 70% of diy rvs. diy rvs almost never have blackwater tanks, always either composting toilets, cassette toilets, or nothing

where will campers dump waste? it matters a lot which system we're talking about

composting-toilet waste, as i said, can easily go into the normal municipal solid-waste stream, same as disposable diapers, but with less smell and health hazard

cassette toilets can be easily emptied into any sewer-connected toilet. when i lived in the usa, most gas stations, supermarkets, and restaurants had toilets with sewer hookups; also highway rest stops and for-profit truck stops (flying j, love's, etc.) also, if you have any friends who have houses, even a single one, you can dump it into their toilet. or pay for a hot-sheets motel room once a week and use theirs

blackwater-tank systems, you're gonna have to drive to the koa kampground or a truck stop 2–4 times a year

I feel this every time people complain about homeless people in LA pooping on the sidewalk.

They have no legal access to a toilet, so where do you think they are SUPPOSED to poop?