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What Percentage of Water that Goes Down the Drain is Actually Lost Forever?

Water%20faucet.gif Last week, peer-to-peer network CurrentTV invited us to participate in their Earth Week special, where they asked their readers to pose their most burning eco-questions to a handful of savvy bloggers. We've been thinking a lot about the state of the world's water lately, so this question stood out to us:

It's always considered a major no-no to waste water. But how is water used in a household wasted? Isn't it all just processed and reused?

I understand that there is energy spent in processing and there are possible chemical issues in the cleaning process but I'm really just interested in the whole concept of "wasting water".
What percentage of water that goes down the drain is actually lost forever?
-- Jakebot

Great question, Jake. We want to answer this question for you in two parts: simple and not so simple. First, the simple answer to your question is zero. Zero percent of water that goes down the drain is actually lost forever because, according to the law of conservation of mass, matter cannot be created or destroyed.

But what you want to know, then, is, 'why is wasting water is such a big no-no?' The answer to that is cost and location. In the United States, most people get their water from wells or from municipal systems. Once they've used it, most people send their "waste" water down the drain to either the wastewater treatment plant or to a septic system. It is costly -- in terms of both money and energy -- to transport water from its source to our houses, and to treat it once it leaves our houses.

Location is a big deal when it comes to water. If you live in Seattle, like we do, it's plentiful enough that we don't need to worry too much about wasting it because there is always enough for all of us to use as we please. But in most places, water still goes through a natural cycle -- either evaporating or soaking into the ground -- before being taken back into the municipal system. So in cities that suffer from drought, there is not enough water in the public system for everyone to use all they want, all the time, and it becomes even more apparent why sourcing water from a reservoir many miles from your home, and flushing it to a location just as far away, is a massive dedication of resources for a system that could be handled more locally.

The costs of operating these systems are growing every year. As Carol Steinfeld, author and founder of Ecovita told us (we asked for her input to help answer your question), "we have more people on the planet, each using more and more water, than ever before in human history." So, to provide the basic human right of clean water for all, it becomes imperative that we get more efficient at using our water. When you think about it that way, it seems very wasteful to use clean drinking water to wash our cars water plants, or spray the sidewalks -- when water re-used once, twice or even three times from relatively clean places like the shower, the sink or the washing machine, would work just as well without requiring nearly as much energy.

Making our water systems more efficient means we need to implement some of our more innovative solutions to reusing and treating our water at the source, such as the super-treatment facilities in San Diego, home rainbarrels, or even Steinfeld's waterless toilets. If we can get better at cutting the external cost of providing clean water -- treatment and transport -- then we can build a system where water isn't waste, but a resource.

Thanks to CurrentTV for asking us to be involved. Check out CurrentTV to see this answer and more during their special Earth Week programing.

Image Credit: Flickr/steelersfan8765, CC License

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The wasted water that is most appalling is the one you've heated. That's why a low-flow shower-head is such a radically cost-effective technology.

Cold water is considerably less important in the grand scheme of things.

Posted by: Daniel Haran on 22 Apr 09

Three things can happen to water to make it "wasted" in my view. I define "wasted" as unavailable to other potential users.

First, it can be broken down into its component parts- hydrogen and oxygen. This is the work of plants in photosynthesis (CO2+H20----> sugar + 02); some chemical reactions, and hydrolysis (H20+energy----> H2 + O2). My slight correction to the above is that conservation of mass does not apply to compounds (like water), but to the constituent parts (hydrogen and oxygen in this case). My sense (but I've seen no good analysis on this question) is that the first two (photosynthesis and synthetic chemistry) are relatively minor in the grand scheme of things. The third is a big "watch this space" item as we look at a hydrogen economy. Nevertheless, the point is that water can, and always is (in living systems) created and destroyed.

The second way water is "wasted" is to divert it from downstream users to down-wind users through evaporation and transpiration. This is reallocation flow in time, space and state (meaning moving it as gas not liquid). This is the vast majority of what is known as "consumptive use." This water is wasted from the perspective of downstream users, but a resource from the perspective of down-wind users.

Third, and last, water is "wasted" when it is contaminated to the point that it can not be used again, or that use imposes costs to use it. This can happen because of pollution (water used to carry waste), or when fresh water enters the sea and becomes saltwater. Freshwater becoming saltwater is the classic definition of water waste on America's west coast.

I do not like the concept of wasted water, as it frames the issue in a way that does not lead to or inspire useful responses. If water is wasted, hoarding is the natural response. We can do better than that.

Notions like wasted water also imply that "use efficiency" is an effective path to solving our (global) water problems. Efficiency is about reducing costs, and slowing the rate that problems grow. At best, efficiency strategies extend the time we have to solve problems, at worst, they lock us into bad practices and distract us from solving the larger, underlying problems. Efficiency strategies are modest first steps, not game-changing solutions.

What we need is a new conversation about effective use of water that will displace the current efficiency paradigm. Think of how you use water today. How many times have you used water for something other than moving waste (shower, toilets, dish and clothes cleaning)? Did you need to use drinking water for all of those? Do we need to use treated drinking water to fight fires or water lawns? These are not efficiency questions, these--and the strategies we can build around such issues--are about effectiveness of water use/management.

Reactions welcome!

Posted by: David Rankin on 23 Apr 09

I was very surprised to read the following statment in WorldChanging especially by two people who I assume are on the staff.

"If you live in Seattle, like we do, it's plentiful enough that we don't need to worry too much about wasting it because there is always enough for all of us to use as we please."

I have been a resource efficiency and sustainability consultant for 25 years working on thousands of projects in the Puget Sound area and in 25 other states.

Why we do in fact need to worry in Seattle and everywhere about wasting water has been the subject of several books and reports and I could give real world examples from the Seattle area alone for several pages.

But, I'll give just 3 examples:

I was hired to consult with one of the largest hotels in Seattle. A hotel that had carried out several water conservation projects. By ultra-sonic metering I found that they used 65% as much water at night as they did during the day. More detective work determined that most of the flappers in the toilets in the guestrooms were leaking. Fixing the leaking flappers saved the hotel over $30,000/year on their water bill at an installed cost of less than $5,000 including labor. That is a return on investment of 600%.

I served for 2 years on the board of one of the water utilities on Vashon Island. One summer when i was on the board, our customer demand for water was getting so great that we got within one week of having to tell people to stop watering their gardens. This request would have killed thousands of plants and killing those plants would have wasted thousands of dollars and at least hundreds of hours for our customers. Luckily at the last minute we finally found the problem, a very large borken underground pipe on a customer's property.

I recently saw an example of a hidden water leak in a bathroom that led to damage that cost a homeowner $15,000 to fix.

There are many reasons to care about leaks including:
- saving money
- ensuring the utility has enough water available to meet peak demand
- protecting the landscape from erosion problems
- protecting yourself from lawsuits that leaks can lead to
- protecting buildings from the water damage that leaks can create
- saving energy in the leaking heated water (as you mention)
- saving equipment that could be harmed
- maintaining public goodwill that is harmed when public agencies have visible leaks
- and on the reasons go.

Hope that helps open a new perspective.

Watershed LLC

Posted by: Michael Laurie on 25 Apr 09

the earth is a closed system...

the concept of wasting water is only valid if we assume that the water that goes down the sink is no longer usable water, why is this?

energy aside, conceptually, the more clean water that goes down the sink to mix with the "used water" the better. But is is only reasonable once we start thinking of the earth as a closed system.

Posted by: stiven on 27 Apr 09

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