The following is the opinion and analysis of the writer:
Frank Bernardi
I am the former owner of a duplex investment property. My tenantβs rent included the water cost since the property only had one water meter serving both units. The average monthly water usage for both units was around 4,000 gallons. Then one month the water usage shot up to 16,000 gallons, a quadruple increase. I thought the 110-year-old underground water supply line from the street had finally sprung a leak! I called the local water department to explain the issue and the customer service representative nonchalantly told me ββ¦sir you have a leaking toiletβ! What, no way a toilet can leak that much water? Of course, I called each tenant, and yes, one of the two toilets was leaking. Itβs hard to know exactly how long the toilet was leaking, the tenant said it was leaking for maybe two weeks. Fast forward to the next water bill, post-toilet repair. The unit's water usage was back down in the normal range!
I share this story because it speaks to the dire water crisis we desert dwellers now face. Our share of Colorado River water is facing a severe cutback in the very near future, and with over 6 million people living in the Phoenix and Tucson metros, itβs imperative to immediately take all means necessary to conserve our precious water.
Letβs look at an example to get a better picture of the potential water savings by repairing leaking toilets. First, after consulting the International Plumbing Code table 2902.1 for the number of required plumbing fixtures (in this case water closets, i.e. toilets) required per various building occupancies (assembly, business, educational, institutional, mercantile, residential, and storage) we find that this number varies from a low of one required fixture per four people in the residential occupancy, to a high of one required fixture per 500 people for the assembly occupancy (for example a passenger terminal). This is a bit subjective, but letβs assume that over the seven various occupancies, the code requires an average of one fixture per 25 people, which is also the business occupancy requirement. Second, based on the metro population mentioned above, that means there are over 240,000 toilets in both metropolitan areas. Third, letβs say 10 percent, or 24,000 of those toilets are leaking. Fourth, if each toilet is leaking 12,000 gallons per month (which is a very conservative number), that means those toilets are wasting 288 million gallons of water, or 884-acre feet of water per month, or 10,608-acre feet per year. The Arizona Department of Water Resources says that one acre-foot of water will serve three single-family homes for one year, thus the amount of water wasted per above would serve 31,824 single-family homes for one year.
We can look at another example, but on a smaller scale. I contacted the Town of Oro Valley Water Utility and asked for the total acre-footage of water delivered to the town for 2025. The utility director was kind enough to provide these figures for 2025: 4,629-acre feet of groundwater, 2,863-acre feet of CAP water, and 1,982-acre feet of reclaimed water, for a total water production of 9,474-acre feet. The latest population figure for the Town of Oro Valley is 49,670. Using the same methodology as above results in the town losing 878-acre feet of potable water per year due to 1,987 leaking toilets. Which means that of the 7,492-acre feet of potable water delivered 12% of that water was wasted, which is enough water to serve 2,634 single-family Oro Valley homes for one year. Interestingly, the total amount of wasted water for the Phoenix and Tucson metros would provide more than enough potable water to serve the entire town of Oro Valley for almost 1.5 years.
Of course, itβs very difficult to really know how many toilets are leaking, but this educated guess illustrates the potential water savings by taking steps to repair this essential part of everyday life.
