Does the shower use more water than the bath?

Q: My husband and I are reducing our household water use, and we pretty much agree on everything except this. He swears his morning bath actually uses less water than my semi-long showers, but that can't be right. Can it? – Marianne, NH

A: That depends on a few things. First, how big is the bathtub? Second, what's the GPM (gallons per minute) rating on your shower head? And third, just how long is “semi-long” anyway? If yours is a newer, “luxury” bathtub, it could hold more than 70 gallons, but most standard bathtubs hold about 50. And really fancy shower heads can go through as many as 25 GPM, while low-flow heads use only a couple of gallons per minute.

For argument's sake, let's say yours is a 50-gallon tub, and you have a 10 GPM shower head. Assuming your husband doesn't fill the tub to overflowing, (and taking into account the fact that he'll displace some water, too), his bath probably uses about 30 or 40 gallons of water. Compare that with a 10-minute shower, which would require 100 gallons! Hubby wins.

But substituting a low-flow shower head really changes the equation. Running a low-flow head for 10-minutes would use just 20 gallons of water—less than even half of your husband's typical bath. You win!

You can see what a difference small measures like low-flow shower heads can make, but before you start conserving water, examine your water bill to determine how much you typically use. That way, you'll have a baseline against which to compare future bills. Some statements report usage in gallons; others report generic “units” that could represent 100 gallons—or even 1,000! Contact your local utility provider to get the whole story.

-         Susan Brackney 

Eco-inquiries, conundrums, snafus? Write to