You should be able to pump 40 gallons into a completely empty 40 gallon tank.
If you're talking how much can be pumped
out of a 40 gallon tank, it depends on how close your pickup tube comes to the tank bottom and if it's in the low corner of the tank. A tilt one way or the other can make a big difference.
You could try to pump as low as your pick up tube will draw, then pull the low point drain and measure how much comes out.
40 gallons of water weighs 336 pounds.
Linear Mode
