I have been deeply tempted to use this. There have been times when I didn’t even tag the disposal not because it slipped my mind, but because “pitlatrine” is wrong.

From the wiki for toilets:disposal=pitlatrine, “waste falls into a lined or unlined pit”. This is a lie. A pit is an unlined hole in the ground. A pit toilet uses an unlined hole in the ground. A lined hole in the ground is a vault and the difference is important to land managers and, I would argue, the end user.

As to land managers, one example would be the United States Forest Service. If an area has over a certain number of visitors a year, they try to supply a toilet facility. If that number is still few enough, a (unlined) pit toilet is sufficient. Over a certain amount, it needs to be a vault. This is due to the waste leaching into the surrounding soil with an unlined system. With sufficient volume, it’s more likely to cause contamination in the area.

When a pit toilet is full, the land manager digs a new hole, moves over whatever construction they’ve got in place to help you stay above ground while you make your deposit, and cover over the old hole. When a vault toilet is full, someone comes to pump that thing out and it stays just where it was before.

For the end user, well, the stories I could tell you about using a pit toilet. The floor of the one in Little Round Valley sagged as I stepped into it. Volunteers had just finished digging the hole and moving the little building over it at Santa Cruz Guard Station as I arrived. Practically smell free throughout the stay! Most of the rest of the backcountry pit toilets in the area don’t actually have full buildings, just 0-3 privacy walls around a topped hole. When not spacious by not having a complete set of walls, they tend to be exceedingly tight. The building of one near Blue Lakes was so tight, it was hard to stand to pull up my pants without opening the door.

I don’t have these kinds of stories about vault toilets. The horse parking one at First Water was getting pumped out when I was there. I’ve got some on how people treat vault toilets, but that’s not about just the toilet itself. They’re a much more uniform item, being a larger construction. Usually they’ve got sufficient room for a wheelchair even if it would be hard to get a chair up the step outside.

I expect there’s a few others thinking as I do. There’s 102 improved_pitlatrine and another 45 blair_ventilated_improved_pitlatrine. No one has gone for vault yet. It’s universally used by the Forest Service and Bureau of Land Management, but that doesn’t make it the UK usage. They are far outweighed by the 65362 uses of pitlatrine, but most of my own uses and some where I have not tagged would be better as vault, at least if we were using American English. (I’m not keen on improved_pitlatrine simply because it doesn’t say how. One (unlined) pit toilet I encountered was outfitted with a lid several decades old that proclaimed itself patented and capable of fitting tightly to prevent flies and smell! Improved, but not meaningfully. On the other hand, vault is very specific to the disposal.)