Illustration by Angelica Alzona/GMG

This is a story about semen and fact-checking.

In April, in my capacity as a dirty-minded cleaning expert, I was a guest on Sex Lives, New York magazine’s podcast about, well, sex. The show’s host, Maureen O’Connor, asked me to join her to take listener calls and help to answer questions about sex messes. One question had to do with the etiquette of where to jerk off when you’re a guest in someone’s home:

I enjoy masturbating, frequently. As in, usually once a day, if not once a day then once every two to three days. So if I’m staying at someone’s house for, like, a week there’s gonna be a moment there where I sort of feel like I need to masturbate. So how would you recommend going about that without being super weird and literally realizing that you’re masturbating in someone else’s house. Any suggestions would be welcome, because this is a little bit of a nightmare to figure out otherwise.

As part of our discussion about the etiquette of where to jerk off when you’re a guest in someone’s home, we touched on the old “semen will clog a drain” chestnut.

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Have you heard this one? The one about the sement? It goes something like this: Semen, when mixed with water, will turn glue-like and block a shower drain right up. This is a thing that is usually trotted out in late August-early September when notices go up in college dorms across the U.S. chastising residents for depositing such an abundance of male ejaculate into the communal showers that the drains clogged and backed up.

The thing is about these notices is that they’re fake. Well, more accurately, they’re pranks.

And, honestly, as pranks go, this is a pretty good one. But while the college dorm notices aren’t demonstrably fake, the matter of whether the accumulation of semen will actually clog a drain is one that remained a bit of an enduring mystery. In fact, it was a subject I’d been asked to look into for a column that ended up getting spiked before I could complete my research. So when, on Sex Lives, Maureen suggested that the caller simply take care of business in the shower—a place where we’re already expected to disrobe, and which offers sound cover in the form of running water—I piped up to say that maybe that wasn’t such a hot idea.

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Ultimately, we agreed to cut that portion out of the episode, and here’s why: I hadn’t done a full deep dive into the research, and Maureen had unearthed a Slate article that stated definitively that semen will not clog a drain. Not wanting to risk putting inaccurate information out into the universe, we tabled the question to give me time to commit to the research that I’d started. The plan was to revisit the subject when Maureen guested on my podcast, Ask a Clean Person, a month later.

During that original cursory look into the matter of semen and shower drains, I found some compelling explanations of the supposed phenomenon. But, source-wise it was no good, because the source was Reddit. And here’s where the fact-checking part of things comes into play: There’s a set of terms used in fact-checking, red check and black check, to categorize sources by trustworthiness. A red check is as close to an infallible source as possible, like Encyclopaedia Britannica or Baseball Reference. A black check, by comparison, is a trustworthy source, such as a newspaper article, that nonetheless cannot stand on its own. You need two black checks to equal a red check.

You probably don’t need me to tell you that Reddit is neither a red nor a black check. But Reddit, much like Wikipedia, remains useful to fact-checkers or the fact-checkingly inclined, in that there may be kernels of information that serve as a jumping off points. And that’s what happened with me and the semen/shower drain question. From Ask Reddit:

Actually there are two competing forces at work here. Semen is composed of sperm, water and several proteins and enzymes. One protein is a coagulating protein, the purpose of which is to make sure that the semen stays in a mass inside the mate and doesn’t run back out. One of the enzymes is a de-coagulating enzyme which is supposed to dissolve the coagulating protein after some time, releasing the sperm bound up in the coagulated mass. This combination dramatically improves the chances of impregnation. In the shower the de-coagulating enzyme gets washed away rather quickly, leaving behind the coagulating protein, thus instant spermy glue. As some have noted, the temperature is not critical. However, how many times you’ve tried this in a day does matter. It takes time to produce the coagulating protein (and everything else but apparently especially the protein). After the first one or two tries, your semen is going to appear much more watery (very little protein) and have a lot less cloudy whiteness (much less sperm {whiteness}). And of course, the younger you are (assuming you’re past puberty) the faster you recover your stickiness.

I mean, it sounds … compelling, right? Certainly, on its own a random post on Reddit proves nothing, but the mention of a coagulating protein was a nugget of something I could work with. Especially because there’s what I already know of protein, which is that it will harden quickly and can be tricky to clean once it’s dried (think about cleaning egg residue that’s been left in a pan).

Still though, Reddit isn’t a trusted source, so that was really only a jumping off point. And the Slate article debunked all of that convincing-sounding science:

Abraham Morgentaler, an associate professor of urology at Harvard Medical School and the director of Men’s Health Boston, debunked the rumor for us once and for all. In an email to Slate, Morgentaler says that not only is semen never thick enough to clog a drain, but that 20 to 30 minutes after ejaculation, it will become a runny liquid and slide away:

When a man ejaculates, the fluid first comes out like a gel, with a certain amount of consistency that likely helps with fertility by allowing it to stay longer within the vagina than if it were a runny liquid.

For this reason, a semen analysis is never performed immediately on a fresh specimen. The lab technicians need to wait until it becomes a liquid, which takes 20-30 minutes.

As a rule, semen just isn’t thick enough to clog a drain. And after a short time it will become runny like water anyway.

That’s all good and right, yes? Quoting a Harvard urologist certainly sounds like a trustworthy source. Sure, but there’s another twist in this fact-checking tale: Not only is Slate only a black check, Slate is a publication that’s known for adopting a contrarian stance. This is colloquially referred to as The Slate Pitch*, and it undermines Slate as a source, in the same way that the political bias of Fox News or MSNBC makes those sources flawed. And there’s not that much literature out there on the matter of semen’s effect on a shower drain beyond those very funny but not-at-all-real dorm notices from campus maintenance.

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If I was going to solve this mystery, I needed sources of my own to speak to the biochemical makeup of male ejaculate and how it behaves when it comes in contact with water. It is not, it turns out, that easy to find experts to talk about jizz. (Present company excluded.) But I’m nothing if not enterprising, and find sources I did!

The first, Dr. Joseph Alukal, is the Director of Male Reproductive Health at NYU School of Medicine, responded to my query with the following:

I remember the [Slate] article. Urologists specialized in our field tend to send these kind of things around.

I also know Morgentaler well; turns out he’s absolutely right. There’s no chance it will clog a drain (liquefaction after about 20 min is a well described phenomenon).

And the second, Diane A. Kelly, a biologist who studies reproductive anatomy at the University of Massachusetts, Amherst. Diane had this to say:

So normally I focus on the structural mechanics of penis function (that is, erection and how it works in different animals), but as it happens, I gave a theoretical talk about ejaculation at the APS Fluids meeting last November, so I have some papers in my files you might find useful.

As you may have already found out, semen isn’t simple. There are sperm cells, for sure, but they’re suspended in a fluid with a complex cocktail of ions, sugars, and proteins. Some of these molecules act as coagulants, others as liquefiers. And their behavior was pretty well characterized back in the 1980s: shortly after ejaculation, semen coagulates into a gel — possibly to maximize its time next to the cervix? — but over the next 5-30 minutes it liquifies. Since the papers say it liquefies equally well in in vitro tests as in vivo, I expect that even if some semen got washed into a shower drain in the gel phase, it’d be liquefied before its source finished shaving.

So there you have it: You can totally jerk off in the shower.


If you’d prefer the aural version of this tale, Maureen did indeed join me on my podcast for what my co-host, Dave Lozo, described as “the most perverted Scooby Doo episode of all time.”

Click here to view this embed.acast.com embed.

It was certainly not an accident that it happened to be Episode 69.