Grey Water Toilets

Water is something that we all take for granted each and every day.  We turn on the faucet and there is clean water there.  Not all countries have this luxury.  Not all people are awarded this type of security in life.  By implementing a grey water toilet in the home, the average American household can save thousands of gallons of water per year.  Grey water toilets are ways to use lightly used water in the toilets because of course perfectly clean water is not necessary in order to go to the bathroom. In this post we’ll take a look at just how much clean water is used by a typical household just to operate a toilet.  We will then look at how simple and financially reasonable it would be in order to install a grey water system in your household.  Lastly we will look at how much clean water you can personally save by implementing a grey water toilet system in your household.

According to the EPA, 26.7 % of the average household’s water usage goes to operating toilets.  This is by far the largest water consumer of any other component of the household. Knowing that we use an average amount of water per day of 400 gallons we can see that:

\[400 \text { gallons per day} \times 0.267 = 106.8 \text { gallons per day for toilets alone} \]

This of course is only a daily amount.  If we look at the entire year we see that:

\[106.8 \text { gallons per day} \times 365 \text { days per year} = 38,982 \text { gallons of clean water!} \]

To put this in perspective, that’s enough water to fill more than 15 twelve foot above ground swimming pools! Clearly, there must be a better way to use all of this perfectly clean water.

Enter the grey water toilet system.  What exactly is grey water you may ask?  Grey water is lightly used water such as the water that goes down the drain after you’ve washed your hands, taken a shower or washed your clothing.  Clearly this water is not suitable for drinking but that doesn’t mean it needs to be wasted.  All of this “waste” water can be re-purposed so that clean, drinkable water does not have to be used in its place.  Let’s face it, toilets do NOT require clean, drinkable water in order to serve their purpose.

This is a basic schematic of a grey water toilet system:

Greywater System Water-Reuse System Schematic

Source: Grey Water Toilet Schematic

As you can see, the system is relatively simple to install.  The majority of the cost of the project would end up being the system itself with a small fee being added for the installation.  The idea is quite simple really: Divert lightly used water to area where it can be used again.

Now lets look at the economic side of grey water.  Can it really save you money?  According the The Guardian, a respected British news company that frequently runs Consumer Report style investigations on a variety of products found that some grey water systems can go for as little as one thousand pounds with installation fees of around three hundred pounds.  So for a total of thirteen-hundred pounds we can see this is equivalent to:

\[1300 \text { pounds} \times \frac { \$ 1.43}{1 \text { pound}} = \$1,434\]

Now looking at the cost of water per gallon in Pennsylvania we see that water costs 1.0214 cents per gallon.  Knowing we waste 38,982 gallons yearly we see we save an average of:

\[38,982 \text { gallons} \times 1.0214 \text { cents per gallon} = \frac {39,816.21}{100} = \$ 398.16 \text { per year} \]

Now of course there are some maintenance fees for this system but they only average around $50 per year meaning the actual savings on water is $348.16 per year.  Looking at the payback time we see that your investment will have payed for itself in only:

\[\frac {\$1,434}{\$348.16} = 4.12 \text { years}\]

This means that after a little more than four years your grey water system will have payed for itself.  After this four year payback period all of the saved money can be thought of as “profit” on your investment.

So the question remains, how much water can I really save?  Well let’s say you’ve just graduated and move into a new home and live there for twenty five years.  Based on our previous calculations we can see that this is equivalent to saving:

\[38,982 \text { gallons} \times 5 \text {years} = 194,910 \text {Gallons of Water!}

Saving almost 200,000 gallons of water over the lifetime of a SINGLE household is truly noteworthy.  So when comes the time to purchase a new house when you graduate from college, see if you can find a home with a grey water toilet already installed or perhaps consider investing in a grey water system as you are investing in a home.

Grey water toilets are a great way for each household to reduce their water consumption.  If each household could implement one of these systems, the United States would overwhelmingly reduce water consumption.  It is the goal of people like us to make systems like these more available to the people so that we can become a more sustainable society.




  1. “About Rates.” About Rates. PA American Water, 2016. Web. 19 Feb. 2016.
  2. “Currency Calculator Converter British Pound to US Dollar.” Currency Calculator (British Pound, US Dollar). X-Rates, 2016. Web. 19 Feb. 2016.
  3. Division, Building Codes. “Water Conservation Systems.” OREGON SMART GUIDE(n.d.): n. pag. Building Codes Division. Oregon State Government. Web. Jan. 2016.
  4. Ferguson, Donna. “Greywater Systems.” Greywater Systems. N.p., 21 July 2014. Web.
  5. “How Much Water Is in Your Pool?” How Much Water Is in Your Pool? Robelle, 2016. Web. 19 Feb. 2016.
  6. “Indoor Water Use in the United States.” US Indoor Water Use. EPA, 2016. Web. 18 Feb. 2016.
  7. Murphy, Melissa. “How to Flush With Gray Water.” Home Guides. N.p., n.d. Web. 17 Jan. 2016.
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