Holding Tank Draw Pipe

[idearat]

Hi folks. I'm doing a new holding tank, to be emptied via a draw tube from a fitting on top. I'm using 1-1/2" ABS for the draw pipe, through a Uniseal.

My question is about the bottom of the draw pipe. I know it needs an angled cut so that it can suck up the... chunks... but I'm not sure how big an angle makes sense. For now I've cut it to just under 45 degrees, which gives about a 1" clearance to the highest edge. That will leave 1" of water / waste in the tank at all times, which I'd rather not have (though the tank's at a bit of an angle, with the draw pipe at the bottom edge, so it won't be the whole tank).

Does it sound like that's the best plan? Do you think 1" is enough? (I'm using a manual toilet and no macerator.) Could I get away with less?

Thanks for any opinions!

Perry.