Installing black water tank

Everything is a compromise. I think best would be toilet over deep end, just so less water is needed to keep things wet. And best for draining tank would be have the hole in bottom instead of side. That way as the level drops, the pipe would stay full longer.

Realistically, I don't think it matters very much where you place the toilet as long as the hole and the toilet line up. You are converting a bus, so that alone implies that you understand things. In this case, water is your friend. After dumping I add approx 5 gal of water, this will eliminate virtually all black tank problems. I try to let the black tank get nearly full and then dump, this gives a powerful flow that evacuates practically everything.
I usually dump just a little grey water first, so that I can see if I have a leak or any other problem. If all seems ok, I let the black water flow, followed by a tank full of grey water to wash out the 3" sewer hose.

Class A Customs 40 Gallon RV Waste Black Water Holding Tank WT-4000 https://a.co/d/bbs0yyL

Above is the link for the black tank we purchased.

Thank you. Yes,we are converting a bus to an RV so this is a new install. Thank you for all the input. Much appreciated.

I haven't re-hydrated any but others that have dealt with the problem didn't seem to think it re-hydrated that easily. At any rate, keeping it wet resolves the problem and has kept me from having to find out the hard way.

Dried poop is only like concrete when it is dry. If you put it in water it will re-hydrate. The issue is when people try to conserve water by using only a tiny amount of water to flush. Or they leave the black drain valve open and try to use like a residential toilet.

Short answer, don't do the two things above and you will be fine no matter where you put the hole in the tank.

Usually, we would cut the hole to line up where the toilet is, but you don't seem to be concerned about that so you must be remodeling.
I would place the toilet over the deep end, because of the chance of water not covering the shallow end at some point. The deep end is where water is most likely to be. Dry poop will turn to concrete and you don't want that.

johnhicks wrote:
Isn't it going to be dictated by where the toilet is?

Or the placement of toilet dictated by shape/placement of tank?

Our rolling oasis...What is the year, make and model of your RV?

On my trailer the the tank slopes from shallow on the ends to deep in the middle. Hence the toilet sits over the shallow end. I doubt it really matter which end yours is over. Use water for the flush and don't dive it a second thought.