This Instructional Activity is a part of the Lesson 15, Unit 2, Grade 7. When students are finding values to aid in their method, consider allowing them to research typical values online at hardware websites or search for values that would be useful. If these tools are not available, some values are provided here. Values that may be useful for students: Typical (modern) shower heads have a flow rate of 1.9 to 2.5 gallons per minute. Older shower heads (pre-1992) could have flow rates up to 5.5 gallons per minute. Bath tubs hold approximately 120 to 180 gallons of water when completely filled to the top.