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Comment by cassianoleal | Hacker News Reader

Ceramic filters are very common in Brazil, used in clay recipients which also keep the water cool even in summer without spending energy.

https://g1.globo.com/saude/noticia/2026/03/14/filtro-de-barr...

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Sri Lankan here. We've had this type of ceramic filter here for at least 35 years: https://cdn.shopify.com/s/files/1/0182/4859/7582/files/Ultra...

Definitely. I think considerably more. I have seen the ceramic ones that seem to be a design that goes back to Victorian ones.

https://en.wikipedia.org/wiki/Ceramic_water_filter

In the Sri Lankan context filters are more important than ever, but I think activated carbon ones? Water is (heavily, I think!) chlorinated but pollution is pretty bad.

Oh yeah I never claimed it was new tech. I can say with some certainty that it's been popular in Brazil for a lot longer than 3 or 4 decades!

This sound like Ghara https://en.wikipedia.org/wiki/Ghara which is very common in rural areas in subcontinent. It keeps water cool in summer. It gives water a very nice earthy taste. Ghara is usually paired with a clay bowl to drink water.

If you can buy a clay bowl or glass, get it and keep water in it on your side and drink from. It will be cool and will have a very nice earthy flavour. But not all clay pots are same quality. Some are not very porous and won't cool the water or give you different taste.

But there is no filter in the Ghara?

Correct, it does not. It is to keep water cool using similar (or may be same) principle. We also now have similar water tanks with taps (we call them coolers) made of clay. They don't filter but are made with similar stuff as a ghara only shaped like a tank with a tap like those Brazillan ones in parent's link.

Using clay to cool water in the summer is actually the original purpose of olla pots in the Southwest. They cool the water through evaporative cooling

Andy Ward demonstrated this https://www.youtube.com/watch?v=TBos0j0FszU

Doesn't that imply you're losing water?

Yes you are losing water but the phase change energy of water is immense, very little needs to be evaporated comparatively for immense cooling.

Yes it does. But it might be worth it if you have more water than cooling capacity, or if you have an otherwise very dry house that you'd want a little but more humidified.

Grandparents used to have this. The outer surface of the pot is detectably moist, but not by much, the water level wasnt noticeably lower by the end of the day, I'd say much less than a single cup. Their climate was very dry, crack-your-skin-dry, I don't think it would work as well in a humid environment.

The cooler water gets, the less vapor it creates.

Mostly in rural regions, but the 'filtro de barro' water from your grandma's house beats ANY expensive filter you can get, haha!

Agree! The water is so fresh and tasty out of them!

This and the low-tech electrical shower-head are the two everyday Brazilian things that never cease to amaze me.

Being poor sucks but at the same time being poor also makes you find alternative solutions to the incredibly expensive solutions first world countries use today. I really wish Brazil can invest heavily into renewables and free itself from oil and electrify even more of everything we do.

> electrical shower-head

Is that for electrically heated water?

I know that in the US on-demand electric water heater uses an enormous amount of electricity, like 100 amps.

Brazilian electrical shower-heads use 20 to 30 amps max.

At what voltage? (I understand Brazil has districts with both 127V and 220V mains.)

https://www.worldstandards.eu/electricity/plug-voltage-by-co...

Homes on districts that use 127v also have a second phase for 220v, mainly for shower heads, electric ovens, etc. Commercial property always have 220v.

Then they don't heat same volume to same temp, it's thermodynamics

Yes but they are also less efficient because they don't have point-of-use placement

wow, 20-30 amps at the shower head... that sounds a little frightening

point-of-use electrocution

Reasonably safe with ground fault circuit interruption.

The passive cooling is almost as clever as the filtration

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