I have a 1000 gal. tank with 4 laterals. My "as built" plans are not consistent with the actual installation of my system. For this reason, pulling measurements off the tank outlet line have not made it possible for me to lacate my distribution box. 

Do you have any suggestions on how I can go about locating my "D" box so that I can inspect it and intall a riser at that point?

Any information would be greatly appreciated.