Q. Are there any hard and fast rules when it comes to flushing your toilet after every visit? Now that I’m a bit older, I find that I may have to visit the loo one to two times a night, and I do not like the idea of wasting the extra water. My spouse freaks out about the non-flush-waiting-for-the-next-time-to-flush habit I’ve begun. If I am just “making water,” is it hygienic to let it sit (as it were) there until the next time? 

Infrequent Flusher
Fort Wayne, Ind.

A. Dearest Infrequent Flusher,

Occasionally, I am called to serve not just as an eco-columnist, but also as a marriage counselor. I believe this is one of those times. So let’s keep our “I statements” in mind as we explore this bathroom battle. What I’m hearing is that you think flushing the toilet after every contribution is wasteful; this makes your spouse feel grossed out, yes, but also perhaps disrespected or ignored. See how these domestic disputes are always about so much more than a little pee?

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The “selective flushing” policy (“If it’s yellow, let it mellow,” as they say, or, in the Caribbean, “In the land of sun and fun, we do not flush for No. 1”) is held dear by many a water-conscious bathroom-goer. In fact, I’ve advised it several times as a smart way to conserve water. Anecdotes are not science, IF, but I personally know plenty of people who have mellowed their yellow for years without any troubles. Despite what cleaning product commercials might have you believe, the practice is not weird. But is it unhealthy, as your spouse fears?

I think a few neutral facts will help you two work this out. One, the substance in question isn’t quite “water,” IF: It’s water mixed with substances excreted by the kidneys. Those include nitrogen, phosphorus, and potassium; salts; and traces of any pharmaceuticals we happen to be taking, to name a few — more than 3,000 chemical compounds in all. And though most of us grew up hearing that urine is sterile, at least one recent study reveals there’s actually some bacteria in it.

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That said, it’s quite unlikely that you’ll catch anything from the liquid contents of your toilet. For one, you’re not actually touching the inner bowl (right?). Even though BYU researchers have documented the artfully named phenomenon of “male splashback,” (it’s exactly what you think it is), as long as everyone washes his/her hands after a visit to the powder room, you all should be golden. And here’s an interesting wrinkle: The act of flushing, not not flushing, is really what can spread germs around the bathroom, via an unappetizing airborne spray.

So if selective flushing isn’t really unhygienic, is it dirty and/or stinky? Well, if you’re healthy and well-hydrated, your No. 1 shouldn’t have strong color or odor. And if you clean your toilet regularly, you shouldn’t be seeing any strange buildup effects in the bowl. Going a few rounds between flushes, then, shouldn’t be unpleasant.

What it should be, on the flip side, is a significant water saver. A standard throne uses 1.6 gallons of water per flush (even less if you have a WaterSense or dual-flush toilet), so if you flush three times a night, that’s 4.8 gallons down the drain. But if you flush every third time, you’re saving 3.2 gallons of water per night, 22.4 gallons per week, 89.6 gallons per month, and 1,075 gallons a year — my, how it all adds up.

You asked if there are hard and fast rules about the Mellow Yellow Policy, IF, but I think that’s for every household to decide on its own. (I do hope readers with their own house rules will share in the comments.) Given all we’ve just discussed, you and your spouse now need to figure out a plan you’re both comfortable with. If your partner is still squeamish, maybe you can start with flushing every other time and build from there. Perhaps you can agree to suspend the practice when you have company. Here’s a tip for your negotiation: Promising to take over the toilet-scrubbing task can buy you a lot of goodwill.