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Comment by _delirium | Hacker News Reader

Although I thought the insistence on running pipes was a waste, it turned out at my university to be a good thing they installed the pipes (capped off initially) even though they were installing waterfree urinals, because after they kept clogging up and cost way more in maintenance costs than they were saving in water, they switched back to low-flush urinals. If they hadn't run the capped-off pipes initially, they would've been stuck.

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It seems as though if they're properly (and regularly) maintained, they don't clog. Sounds like your university's periodic (compared to acute - think janitor) maintenance workers were improperly trained on how to care for them. The second page of the article explains this.

(edit: on second thought, it was a university. Knowing what university students tend to put in urinals, I'm not surprised they clogged even with proper maintenance)

They should design a "self cleaning" model that actually uses the piping behind the urinal to flush once a week or so. It seems like this would resolve the need to rely on human maintenance, although the urinal wouldn't truly be waterless anymore.

I agree it's probably possible to maintain them well, but it seems it's still a cost. If nothing else, you have to pay for better maintenance workers, or more oversight of them.

I've seen these toilets in action and from my few encounters, they work as advertised.

But after reading about how they work, I have reservations on the design. Depending on maintenance for keeping sewer gases from escaping seems failure prone. Humans err (and get lazy). I'd much rather depend on plumbing codes that have been tested over decades and work "automatically" than depending on changing a cartridge.

What happens if a bathroom with a waterless toilet is abandoned or isn't maintained regularly?

The traditional U-trap can fail if abandoned or isn't used regularly too. The water eventually evaporates.

Happened to me regularly when returning from summer holidays.

To prevent it, put a small amount of mineral oil (baby oil) in the trap.

It will float on top and prevent the water from evaporating.

I guess vegetable oil should also work? By the way, I heard of the same trick for keeping water in your vases.

Vegetable oil will oxidize and turn into a sticky mess.

OK, thanks.

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