Your question is unclear.  Assuming the tank is vented to atmosphere, then the pressure buildup depends on the depth of the water in the tank, which depends on the shape of the tank (tallskinny tank means more water height with higher static head (pressure) for the 1000 gallons of water in the tank).  Assuming it is not vented (like many water surge tanks in residential systems), then pressure will buildup as the tank fills.  You can use the ideal gas equation to calculate.

About 74".  1 foot = 12 inches = 30.48 cm.  12/30.48 Inches per centimeter