Determine key measurements for a septic tank installation. Here are the facts: The sewer line from the house is sloped at 1/4" per food and travels 20ft to the tank. The pipe invert (bottom) starts 12" below ground. A 6" sand bed will be installed under the tank. The tank will be a 6" single wall 1500 gallon tank.

Find the following:

1. Drop in pipe level (inches) to the bottom of the septic tank inlet.
2. How deep should the tank excavation be so that the house drain lines up with the tank inlet?