Can You Save Money On The Water Bill By Only Flushing The Toilet After Pooping?

Let's talk about peeing, pooping, peeing and pooping, flushing pee and/or poop, and giant spiders. We're kidding about the spiders, so this conversation should be a breeze. What we are here to figure out today is what appears to be a simple question: Is it possible to save money on your water bill by only flushing the toilet after pooping, and not after merely urinating? The answer seems to be a resounding, "Well, duh, of course it does." But a better and more interesting answer is something like, "It depends on a lot of factors, and saving money isn't the only reason to conserve water."

First, we should flush out any absolutes that make this conversation irrelevant. For example, does urine sitting in a toilet for eight hours pose an imminent health risk? North Carolina's state epidemiologist, Dr. Jeff Engel, told an ABC affiliate back in 2007 that it does not. "Letting it mellow" has actually been a water-saving strategy since at least the California drought of 1976-77. But it's not clear that it's also a reasonable approach to saving money instead of, say, installing dual-flush toilets or dozens of other easy ways to conserve water in your home.

As we've already said, flushing the toilet costs a little money. Very little, it turns out. The EPA's WaterSense standards are based on EPA estimates for the cost of delivering and, later, sewering away 1,000 gallons of water, which it figures is about $12.60. At 1.28 gallons for the average flush, you're looking at the better part of two cents per flush. Whoever does the toilet cleaning might have some opinions about this level of savings. But that's just one flush. What about the bigger picture?

Our own back-of-envelope calculations make it sound like a much bigger deal. Assuming a person sleeps eight hours without urinating, at least in a toilet, and assuming everyone urinates once every two hours (the going rate for children, though adults usually pee less frequently), you get nine bathroom trips per day. Multiply that by 1.6 gallons, the current industry standard flush size, then multiply that by the number of people in a household (we'll use the national average of 2.57). All of that gives you the amount of water used for flushing in a household per day. Multiplied by an average of 30.4 days per month and then the average price of $12.60 per 1,000 gallons gives you $14.17 per month for flushing water. The average person poops once a day, which works out to about $1.58 per household. That means letting it mellow can save you $12.59 per month.

Of course, the above figure is wrong for you and almost everyone else. Adults don't generally urinate every two hours, your household doesn't contain 2.57 people, and odds are your water doesn't cost $12.60 for 1,000 gallons. The portion of that $12.60 average that's for water (rather than sewer) is $5.68 per 1,000 gallons. Water costs also depend on where you live. For example, as of 2017, Cal Am customers on California's Monterey Peninsula were paying just over $20 per 1,000 gallons. But if those customers seem to be the most likely to benefit financially from skipping the occasional flush, note that residents' conservation efforts resulted in their being charged for water they didn't use, which is allowed under California regulations when Cal Am has a shortfall. Letting it mellow made no difference in their water bills.

There are many reasons besides saving money that you might choose to skip pee-only flushes. Any community facing drought or aquifer depletion, which can result in lower levels of surface and groundwater, might reasonably choose to implement conservation measures to improve the situation. And individual homeowners can face any number of situations that require extraordinary water savings, such as a septic system installed in poorly percolating soil that can't handle as much volume during times of year when the water table is high. Whether you decide to let it mellow is, then, a function of your individual circumstances, values, and preferences. You can save money, but not a lot. Sometimes, though, every little bit helps.