I will be thinking the best way to locate plumbing to above the roof line. I have a bathroom closet I can run a pipe up. I'm thinking I need to form branches in the basement with at least two suction points. Currently my temporary fan is not sufficient to get below a level of 4. With fan off the winter level can go up to 40 (estimated) Summer goes well below 4. I only need to run the fan 1/2 the year. I installed a temporary fan last year when I found the level going above 20. I plan on digging up concrete this summer when I try to install a new bathroom, and I will probably scope out the gravel and dirt below the concrete. That should be REAL fun. The other thing, my 160 CFM fan is probably sucking 20 CFM, s I don't need 3 inch piping. 1 1/2 should be plenty. I may also need to vent some of the cinderblock walls.