Yeah Vince, thats for a LARGE leach bed. Not our size.
Joe, yours sounds complicated. You may have a dosing tank after the septic tank. But code has changed so much all that was probably required. Mine was built in 76. My distribution box is a plastic cylinder with a plastic lid. Either way, Vince has got it, the lid farthest from your house will be the distribution box.
Just to give you an idea also, you and the wife (assuming 4 bedroom house [500g/br]) will not fill a 2000 gallon tank in 21 months. It took 4 of us 6 years to fill a 1500. (2 adults 2 kids)