Dry vacum tubing size?

[Fox Run]

What sthe size of tubing need for running a dry vacum line. We are lookng into putting in a whipping dry vac system and i've heard for dry vac line, it needs to be one tubing size larger than the vacum line? We are running 1000ft of 1 1/2" then reduced down to 1'' for the next 2000ft for our main line, with 3/4'' lateral lines Tee-ing off from it. Any help would be appreciated.