We find them in airports and other public places where the threat of sharing a toilet with those who may defile it is all too high. You sit down, you do your business, and you leave; the magical electric eye knows when you've left, and suppresses the evidence accordingly.

The many faces of the autoflush sensor. Are any of them out to get us?

But like all technology, autoflush sensors are a double-edged sword -- they're great when they work, but when they don't, they create a problem far worse than that which they solved in the first place.

The overzealous autoflusher is the Turd of Damocles that hovers menacingly over public toilet use. Maybe it's one out of ten, or one out of a hundred, but there's always one, waiting for you to shift, squirm, or just clench your cheeks too hard -- any excuse to release itself in an ass-bathing torrent or, if you lean forward to avoid it, a back-splattering flood of dungwater.

They masquerade as innocent toilets, and don't reveal their true nature until it's too late -- you're halfway through your constitutional, and there's no stopping now. Your choices: ride it out, trying to find that one body position that doesn't set off Old Faithful; or waddle, ass dripping and pants 'round ankles, into the next stall, and pray this one isn't out to get you as well.

There must be a better way. Surely this problem with the valves is known to those who created them. Can they save our asses?

If one judges by web presence alone, Terry Love [1] is Seattle's premiere plumber. His site is comprehensive and entertaining; surely, if any man knows the Secret To The Autoflush, it is him. Speaking to Terry about this issue, I learned that businesses don't install autoflush valves purely for the convenience and sanitation of the user. "It's not only sanitary, its practical," Terry told me. "The less you can get people to touch your stuff, the longer it'll last."

Terry elaborated. "A lot of people flush with their shoes. You've got guys who put all their weight on the flush valves... I don't know what that's going to do to the pipes in the wall. They're not designed to support the weight of a person. And kids will go in and flush flush flush... keep hammering it." He paused and laughed. "I've done that before."

Unfortunately, Terry could offer no insider's advice to those trapped on top of Mount Splashmore. Since his primary focus is residential plumbing, Terry has little more technical expertise with autoflush valves than any other bathroom civilian. "I haven't had to work with them yet... I'm just a user."

Terry suggested I might get answers by contacting those responsible for the autoflush valves directly. Following his advice, I spoke first with Steve Bronson, owner of Air Delights [2], one of the largest distributors of autoflush valves in the country. He explained the mechanics of the autoflush valve: "An infrared sensor on the battery-operated unit detects motion, and a magnetic solenoid that attaches to a push rod activates the flush. When you step up to the unit, you break the beam. The unit knows that someone has broken the beam, and once the user gets out of the path of the beam, it activates the flush."

Mounted on the top or the side of the flush valve, the infrared beams are adjustable to pick up movement from 8 to 54 inches away, depending on the manufacturer. When the beam is broken, the unit does nothing -- it waits until the beam is again whole, waits a few seconds to make certain the user has left the unit, then triggers the flush.

But as John Lauer, Director of Technical Services at Sloan Valve [3], explained, it's more complicated than it sounds. "You want the beam to pick up a sitter, you want to pick up a stander, you want to pick up someone hovering -- but you don't want to pick up the door. So it's difficult, with a lot of variables."

Autoflush valves have been around for a long time -- Sloan Valve has been making them for at least 20 years --so there has been a lot of research into failsafe mechanisms to help deter premature flushing. Ron Bank of Ron Bank Associates [4] described the efficacy of contemporary safety measures. "In a closet {stall} situation, you have literally have to get up and leave to make it flush -- or crouch down and put your head on the floor, that might do it."

All three men I spoke with ardently denied that autoflush valves have any history of turning against their human masters. "Frankly," said Mr. Bank, "we've been selling them in this territory for close to 15 years, and we've never had a complaint to that effect."

Mr. Bronson agreed. "I've been working with these for a long time, and the complaint we mostly get is that they'll flush over and over and over. In my experience, what you just described very rarely happens on the units we offer. It's possible it might happen on other units from other companies, but not on ours."

But it does happen. PoopReport has the stories [5], and many of us have the experience. I pressed each representative to temporarily, for the sake of PoopReporting, accept the existence of the problem, and speculate on probable causes and possible solutions.

They proposed a number of reasons. Faulty installation, perhaps. (Mr. Bank: "We find frankly that most plumbing contractors are not particularly versed in setup. Their main concern is to get off the job as quickly as possible and go home.") Maybe a smudge on the lens. Maybe improper range or angular adjustment of the beam. Or, maybe low batteries -- "It's possible that if the batteries get low, that reduces the effectiveness of the object lock beam," Mr. Bronson speculated.

Regardless of the underlying cause, the result is that the unit flushes because it thinks the beam is no longer broken -- it thinks you've stepped out of the path of the beam. The consensus among the men I spoke with, to varying degrees of certainty, is that the issue could be resolved by ensuring the unit knows the beam is, in fact, still broken.

With this knowledge, a unit on an anal jihad is easily defeated. By placing your hand in front of the sensor, the beam is broken, and unless the problem is with the internal mechanics of the unit, it will refrain from flushing until you've pulled your hand away.

If you don't have the flexibility to finish your business while holding this awkward pose, you can use this temporary flushing reprieve to wrap some toilet paper a few times around the unit -- this breaks the beam so you can pull your hand away. Just make sure to remove the paper when you leave, so future poopers aren't forced to stumble upon the corn you had for dinner last night.

-- Dave [6]

Like Dave? He's featured in The Journal of Ass Production [7]!