Above is a pdf of an exceptionally thorough CBI (Chicago Bridge and Iron) construction manual which consists of information regarding just about everything which a water tower painter (and sandblaster) needs to know about rigging the following tanks:

Elevated Storage Tanks - (1) Waterspheres (2) Waterspheroids (3) Fluted Pedestal Tanks (4) Spheroidal (Curved Shell) (5) Ellipsoidal (Straight Shell) (6) Tripod Elevated

Ground Storage Tanks - (1) Dome & Umbrella Roof Tanks (2) Cone & Sphericon Roof Tanks (3) Ellipsoidal Roof Tanks (4) Open Top Tanks (5) Weathermaster Tanks (6) Hinsdale Roof Tanks

There's also information regarding ventilation.

If you need to you may download our pdf of their manual - CBI - Chicago Bridge & Iron - Water Tower Painter Rigging Guide