residential water use and water footprints

[Hooray!  I have a working laptop again, and most of my data from my previous laptop has been restored.  That means that this week I can finally publish a post that I started writing back when effectivism only existed as the idea of a blog. :) ]

I try not to waste too much water.  In the past two living arrangements I had, my roommates and I didn’t flush the toilet after we peed, so as to save water.  I also turn off the water while brushing my teeth and as much as possible when washing dishes by hand.  At the same time, I love to take longer showers than I need, and I can’t bring myself to turn off the water while soaping — the “sailor shower” that some of my friends advocate.  At some point, I started wondering how all this balances out.  How much water does it save to flush the toilet relatively infrequently?  Just how guilty should I be feeling about standing under the shower a minute or two longer than I really need?  Are there other relatively easy ways to save water that I’m not thinking of?  I decided to do some poking around.

I decided to look at U.S. residential water consumption.  The first thing I noticed when I started looking at water usage numbers is that various branches of the U.S. government and also various local and state governments have put out a lot of different water use calculators and information sheets — and there’s a lot of conflicting information.  By tossing out extreme outliers that appear to be mistakes and averaging the information that was left (sources listed at bottom of post), I arrived at the following average estimates for residential water use (includes also notes about things that I found useful/interesting):

Clothes washing (machine): : 50-60 gallons/load std, 40-45 front load
Toilet flush: 3-7 gallons standard, 1.6 gallons low-volume toilet — Toilet flushing generally makes up the plurality of residential water use, not counting yard & landscaping, at 27% of the household internal water usage.
Shower: 5-10 gallons/min standard; 2-3 gallons/min low-flow
Bath: 36-50 gallons standard; 40-80 whirlpool
Dishwasher: 6-10 gallons/load standard, 3-5 Energy Star or European
Dishwashing by hand: up to 16 gallons/load — dishwashing by hand uses both more water and more energy than using the dishwasher!
Teeth brushing, hand washing, other sink usage: 1-5 gallon/min that the sink is running
Watering the lawn/yard: This depends on the hose size and the water pressure.  If your water pressure is 60 lbs/in2, you can use 10-30 gallons/min that you have the hose running.  Using drip irrigation instead of a hose is 20-50% more efficient — and it also wastes less water through evaporation.  Most efficient of all is, of course, using gray water (water collected from the showers, dishwashing, etc) and rainwater.

The bathroom is where most of the water in the house gets used.  Taking really long showers is not a great choice, but not flushing the toilet as often saves a lot more water than I’d expected, overall. Here are a few other tips I found for saving water that hadn’t occurred to me:

  • Refrigerate a bottle of drinking water instead of letting a faucet flow until the water is cold enough to drink.
  • Use a dishpan or plug the sink when rinsing fruits and vegetables. This water can then be used to water plants. (same is true for dishes, which I’d heard more often before.)
  • Add your garbage to the trash instead of putting it down the garbage disposal. Disposals use a great deal of water and add unnecessary solids to the sewer or septic system. [Another good reason to compost!]
  • Don’t use water to defrost frozen foods — instead, leave them in the fridge overnight to defrost.
  • Boil food in as little water as possible. You just need enough to submerge your pasta and potatoes, and with less water you keep more flavor and nutrients in your veggies.
  • If you’re planning on steaming veggies to go along with rice, potatoes or pasta, put your vegetable steamer right on top of the starchy foods you’re boiling.
  • Set up rainwater and gray water collection systems, but first, check to make sure that they’re allowed by local municipal codes. [?! I didn’t know they might not be!]

The EPA also had some useful tips about how to detect leaks, which can cause a lot of water to be wasted:

  • Challenge: Leaky faucets that drip at the rate of one drip per second can waste more than 3,000 gallons of water each year.
    Solution: If you’re unsure whether you have a leak, read your water meter before and after a two-hour period when no water is being used. If the meter does not read exactly the same, you probably have a leak.
  • Challenge: A leaky toilet can waste about 200 gallons of water every day.
    Solution: To tell if your toilet has a leak, place a drop of food coloring in the tank; if the color shows in the bowl without flushing, you have a leak.

The EPA also has some interesting information about how saving water impacts the environment, and the effects of water conservation on water quality.

Of course, even if we save all the water we possibly can, residential water usage makes up a relatively small fraction of overall water use.  Only 11% of water use in the U.S. goes through the public supply; the majority of water usage occurs in thermonuclear power (48%) and irrigation (34%).  The public supply provides water to over 85% of households in the U.S. (those that don’t have their own private supply), but it also provides water for many industrial and commercial purposes.  So that made me think initially, “Well gee, my water choices don’t really add up to anything!”  Then I started looking at water footprint calculators, which take into account a lot more our indirect water usage as well.

According to a lot of the water use calculators, the average American uses something like 70-150 gallons of water a day, which is a very tiny amount compared to the industrial, irrigation, and power supply uses.  But when you start looking at water footprint, that number jumps to more like 1200 gallons a day per person.  This number reflects a lot more than just residential water use — it also takes into account where a person’s food comes from, what kinds of products they buy and what they do with them afterward, what kinds of transit choices they make (e.g., owning a car means washing a car and also refining the fuel for it), how much and what kind of energy they consume, and so on.  Most of these things also factor into carbon footprint, which we haven’t yet talked about at Effectivism, but the water usage is not always affected in the same way.

Diet makes a huge difference to overall water footprint.  On average, a vegan indirectly consumes 600 gallons of water per day less than a person who eats the average American diet. has a detailed water footprint calculator that takes into account a great deal of information about your diet (be prepared to estimate how many kilograms of various items you eat per week).  Both and H2OConserve also have calculators that don’t get into as much dietary detail; the calculator is more globally useful (I think the other is U.S.-focused).

H2OConserve has a set of tips to reduce your water footprint, sorted by both type/location of water use and also by price of modification (many are free). has a lot more extensive research and information about global water usage, including case studies of how much water it takes to produce various products.  The water footprint for a cup of coffee vs. tea in the Netherlands is 140 liters vs. 35 liters.

The overall message: tea drinkers and vegans rejoice.  ;)  More seriously:  there are a lot of things that aren’t too much of a pain that you can around the house to conserve some water (as well as a lot of things that are a bigger pain and/or cost more money to set up), and there are a lot of things that you can choose to change about your diet or habits  that make a huge indirect difference to water consumption.  I hope this post provides a jumping off point for starting to think about the choices you want to make  regarding water usage.  Of course, most choices we make also have all sorts of other indirect effects, so the water footprint doesn’t tell the whole story.  But it’s a place to start.  If you have questions or things you’d like me to research further, please let me know!

Water use sources:
U.S. Geological Survey: How much water do you use at home on a typical day?
Washington Suburban Sanitary Commission: Water usage
EPA: What you can do
EPA: How do we use water?
Tampa, FL municipal water use calculator
Chester County, PA Water Resources Authority: Water Conservation Tips
One Green Generation: Does using a dishwasher actually decrease water use?
H2OConserve: Water Footprint Calculator
To Inspire and Mobilize: Summary of a study on dishwashers (couldn’t find the original study, but this has a good quote)
Generous: Turn off the tap when brushing your teeth

  • Refrigerate a bottle of drinking water instead of letting a faucet flow until the water is cold enough to drink.
  • Use a dishpan or plug the sink when rinsing fruits and vegetables. This water can then be used to water plants.
  • Use a dishpan or plug the sink for washing and rinsing dishes.

Add your garbage to the trash instead of putting it down the garbage disposal. Disposals use a great deal of water and add unnecessary solids to the sewer or septic system. This also may be a good time to start composting!

1 Comment

  1. Martin DeMello Said,

    February 20, 2010 @ 8:30 pm

    on rainwater harvesting: