Bathtub Faucet

• While showerheads --and sink faucets -- have measurable flow rates, calculating the water usage and waste of a bathtub facet is not as scientific. A larger size faucet pipe -- like a high flow 3/4 inch model -- will provide a higher flow rate, and knowing the psi (pounds per square inch) or water pressure can help determine your flow rate, but this information is irrelevant because the objective of running water in a bathtub is to fill it to a certain point, whether it's halfway or completely filled. A lower flow rate just means it will take longer to get to the desired bathtub level.
  
  

Showerhead

• A conventional showerhead uses anywhere from 3 to 7 gallons of water per minute. However, there are low-flow, water efficient models that use only 1 to 2 1/2 gallons per minute, which significantly reduces the amount of water consumed during a shower. Some models also have flow regulators and cut off valves to decrease or cut off the water during shampooing, lathering, etc., while maintaining the current temperature.
  
  

Showerhead Test

• If you're not sure if your showerhead is efficient, the Department of Energy recommends this test: Find a pitcher or bucket that holds at least one gallon of water and notate the gallon mark if the container doesn't list this information. Put the container in the shower and turn it on as you normally would. Observe how long it takes to reach the gallon mark. If this time is less than 20 seconds, you do not have a water-efficient showerhead.
  
  

Other Considerations

• The true test to determine if your bathtub faucet wastes more water than your showerhead is to take a shower as you normally would and allow the tub to fill with water. Afterwards, check the water level in the bathtub to see if it is higher or lower than when you take a bath. Also, ensure that you don't have a leaky faucet drain. While this won't affect your showers, it will significantly affect how much water is wasted while trying to fill the bathtub.