I have a 15 gallon holding tank
on my Beneteau
, The pump out discharge fitting is located at the lower side of the end wall and thus, it is just above the lower 90 degree corner.
When the boat is pumped out the waste does not completely empty as the 1.5" outlet starts to suck air prior to all of the waste emptying. It is about an inch up the end wall. It must leave about 2 or 3 " inches of waste, that does not seem much however it is about 1 to 2 gallons.
I am planning to build a sloped platform for the tank to sit on so that the waste will run down to the outlet and cover it prior to sucking the last of the waste then air ( no air ).
My question: Is there a suggested slope for the tank, Too much angle might leave solids behind and too little, the waste will not run down hill.
Given the length of the sloped side of the tank is 25" I was thinking about a two inch slope, this does not seem very much.