How do you replace the belt when installing a water pump in a 1989 Suburban?

This should be a serpentine drive belt. If you havn't removed the belt yet make a sketch of how the belt goes over the pullys. Most vehicles now have a drawing somewhere under the hood. The tentioner for the belt is on top and requires a 5/8" or 15mm wrench to pull the tentioner away from the belt. remove the old, install the new. Pull the tentioner away as far as you need to slip the belt into place. Visually follow the belt all the way around to insure it is in place before starting the motor. HTH Stan

If you dont have a belt routing drawing to install the belt go back to your parts store and look in the belt catalog. They have pictures for most all vehicles. Stan