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# How Much Pee in Your Pool?

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The scientists calculated that one 220,000-gallon, commercial-size swimming pool contained almost 20 gallons of urine. In a residential pool (20-by-40-foot, five-feet deep), that would translate to about two gallons of pee. It's only about one-hundredth of a percent, but any urine in a swimming pool can be a health concern for some people, not to mention that smell that never quite goes away.
This is from Erika Engelhaupt, "Just How Much Pee Is In That Pool?," March 1, 2017.

HT2 Tyler Cowen.

Maybe I'm just a glass half full person, or, in this case, a glass greater than 99.99% full, but here's my question for economically literate people:

Does this number for a commercial pool translate straightforwardly the way she says for a private pool? Remember that this is an economic question, not an arithmetic question.

Hint.

CATEGORIES: Incentives

zeke5123 writes:

Of course not. The cost of peeing in a commercial pool is largely borne by third parties (i.e., a negative externality). In contrast, the cost of peeing in a residential pool is more largely borne by the one peeing. Consequently, there is likely to be much less urine in the residential pool.

This assumes the same mix of swimmers in both pools. If residential pools have more small children compared to commercial pools, then all bets are off.

Daniel Kuehn writes:

The percentage is probably an underestimate for the pool my three and a half year old and one year old were in yesterday.

writes:

Given the private pool is a private resource, I'd doubt the math translates the way the author supposes. More incentive to keep the pool clean and free of pee. Likely easier access to restrooms, too. In short, no tragedy of the commons.

I'll offer a quick dissent from the conditionals zeke5123 and Daniel Kuehn provide above. I do not think it'll depend on how many kids use the pool. That changes the clean-up costs, but not the incentive structure. It's probable, in this man's opinion, that the residential pool is still cleaner than the public pool even if the private pool has more children, because the incentive is still there to keep the pool clean.

writes:

Cutting the other way: all residential pools are run by amateurs who are very busy with other things. A commercial pool is run by employees who follow standardized procedures to cycle out water and regularly test the pH of the pool and whatnot. At the local community pools I worked at, this happened at least weekly. In contrast, when my family had an above-ground pool, I'm not sure we used our test kit even monthly, and I don't recall any of the other families with pools testing or refilling them regularly. Specialization of labor.

Rich Berger writes:

I am suspicious of the claim that this sweetener is so directly correlated with urine. I'm also guessing that most of the pools in Canada are indoor pools due to the short summer season which may distort the results.

David R. Henderson writes:

@gwern,
Very good point. Thank you.

Leo writes:

Gwern, my experience with residential pools (inground, fwiw) is fairly different. I'll grant that I never personally check the chemical levels, but the pool cleaner does weekly. I can't prove it, but I think the majority of people who use their residential pool hire a specialist to keep the pool (and water) clean instead of doing it themselves; maybe not weekly, though. Nor can I prove this, but I don't think the difference in cleaning quality/frequency would make up for already-mentioned factors (higher volume of commercial pool use, tragedy of the commons, social norms, difference in bathroom access, etc.) for having proportionally less piss in a residential pool.

Though on the other hand, you're more likely to have dogs or other pets in a residential pool. I have no idea if animals are prone to urinating in the pool, or if that would be significant amount of urine compared to a person. Shrug.

MikeP writes:

In my experience a public pool has a much greater swimmer-hours per gallon. I think that swamps any effect of tragedy of the commons, even though the effect is in the same direction.

James P writes:

I spent a summer doing pool maintenance once (yay youth summer jobs), and from that experience I have to say that whether people hire a pool cleaner depends a lot on the area and demographics. For me, in my (relatively moderately affluentish) area of rural(ish) southern Ontario, most people who hired us to do pool openings in the spring did not hire us to do regular maintenance or cleaning.

(Granted, perhaps our opening services were world-renowned and our cleaning services were known to be so-so, but I have no evidence one way or another on that. And that's not counting those who opted to open their own pools.)

That's just one view from one company servicing one demographic, so take it with a grain of salt. In the Greater Toronto Area or in the American vacation zones, perhaps people are more willing to spend their money on pool cleaning services, but it was not my experience. It's very possible my mileage has varied from other people's.

All of that said, the people who hired us were incredibly particular, however, about how their pools were opened and maintenanced (down to complaints - by farmers surrounded by fields - about dirt getting in their pools), so I imagine residential pool owners are also more inclined to keep people from peeing in their pools in the first place than are recreational pool owners. While their are certainly other factors involved (that others have explained more clearly here), I don't think that, given the tragedy of the commons, we can easily scale recreational public pools to residential pools.

I'm with gwern. The public pools are maintained by professionals. Also private pools may be more likely to be used by children, who are more likely to pee and think nobody will notice.

andy writes:

"It's only about one-hundredth of a percent, but any urine in a swimming pool can be a health concern for some people, not to mention that smell that never quite goes away."

I'm not sure I understand this correctly: do they say that commercial swimming pools have normally urine smell?

MP writes:
gwern writes: Cutting the other way: all residential pools are run by amateurs who are very busy with other things. A commercial pool is run by employees who follow standardized procedures to cycle out water and regularly test the pH of the pool and whatnot. At the local community pools I worked at, this happened at least weekly. In contrast, when my family had an above-ground pool, I'm not sure we used our test kit even monthly, and I don't recall any of the other families with pools testing or refilling them regularly. Specialization of labor.

I was a lifeguard at a public pool in the 1970's, and if by cycle out, you mean completely drain and re-fill, we never did that during the season, but we were open seven days a week, and that would have closed us at least a day, probably two. On a hot, sunny day, we did add hundreds of gallons of water, and we checked the pH and chlorine levels hourly, but that was it. Even if somebody vomited in the pool, we would get everybody out, try to clean it up, and shock the pool with chlorine for a couple of hours.

writes:

The reason that they use artificial sweeteners is that when the rest of the urine reacts with the chlorine it is no longer urine.

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