Mexican Septic Systems
We promised to explain why you should not put paper in a Mexican toilet, and we’re not going to let you down. There are actually several answers to this question and the most puzzling of these is: you can put paper in a Mexican toilet! Yes, you can. The toilet will not spit the paper back out like a wrinkled dollar from a vending machine. The toilet police won’t show up at your door. And there will be no immediate ill effect from your indiscretion.
But it would be rude.
In many tourist destinations in Mexico, especially hotels, where modern sewage treatment is available, you are encouraged to flush your paper, just like in Gringolandia. The hotel management may even post little signs to let their Mexican guests know that they are expected to dispose of their papel confort down the toilet. They have to do this because Mexicans are trained from birth to be very polite.
But away from the tourist hangouts, and especially in private homes, you will encounter a small, covered, plastic or plastic-lined wastebasket near the toilet. If you see one, then be a polite guest and put your paper in there, not down the toilet.
To understand what etiquette has to do with how you dispose of toilet paper in Mexico, we need a basic understanding of sewer systems. If you are reading this from your home or office in Gringolandia, chances are that your toilet (and anything else that drains from your house) is connected to your city’s public sewer system. Everything you flush flows through large concrete pipes to an industrial processing plant where the solids are separated from the liquids. The liquids are filtered and treated with chemicals and the result is released back into the environment in the least offensive way possible where nature finishes the process using evaporation and rain. The solids are also treated and refined, resulting either in trash or fertilizer. This immense infrastructure is quite expensive to install, operate and maintain. It also consumes a lot of energy. These are your tax dollars at work.
Gringos who flush outside the city limits use a private septic tank, called a fosa septica (septic pit) or sumidero (drain) here in Mexico. In Gringolandia, a septic tank is usually made of a durable plastic and has two chambers, each with a pipe tee inside. The first is the sediment chamber, where the wastewater initially enters. User Plawerth explains the process neatly in his comment:
When waste enters the tank, the paper, poo, and any oils from bathing will float near the surface as a layer known as scum. Over time bacteria will consume nutrients in the scum, and it then settles on the bottom as dense sludge, which is basically inert compost.
When liquid enters the tank, an equal amount of liquid flows out the drain pipe. The tee with its long tube extending down below the surface prevents the floating scum from leaving the tank. The upper part of the tee allows methane and other gases to vent out, while preventing soap foam and lightweight scum above the water line from leaving the tank.
Some scum can still potentially pass, though, which is why there is almost always at least two chambers, and sometimes three chambers, each with a tee on the liquid outlet to restrict scum from leaving the chamber. Usually the first chamber contains most of the sludge and the second and third chambers contain little or no sludge.
If the tank is not cleaned of sludge often enough, eventually it will fill with sludge in all chambers, and then solids will start to leave the tank and plug up the leach field.
A filter on the final outlet will help keep solids that are overflowing out from a poorly maintained septic tank from reaching the drain field, but this needs to be a fine mesh plastic screen or a layer of sand, not just a pile of large loose rocks.
Unlike their northern neighbors, almost all Mexicans use a fosa septica, which is not much different than a Gringolandia septic tank. This technology is very old, so the process is the same. The only difference is the materials. Here in Mexico, many of the colonial houses and other buildings were constructed before the advent of plastics, so most fosa septica are built from plastered stone or concrete block. While plastic septic tanks have one or more manhole covers to permit inspection and cleaning, Mexican fosa septica are generally covered with a slab of concrete and sealed with plaster, like a tomb.
The important difference between a traditional, Mexican fosa septica and a plastic, Gringolandia septic tank is what happens when the clarified liquid is released back into the environment. In the plastic version, the liquid enters one or more perforated PVC pipes, which are buried in long trenches about four feet deep, filled halfway with gravel and covered with topsoil. This is called a drain field, and it’s where you want to plant your strawberries.
In the traditional, Mexican version, the liquid flows down into a filtro (filter), which is a concrete-lined pozo (well) filled with several inches of gravel on top, followed by several inches of charcoal in the middle, followed by a foot or two of sand at the bottom. Why use a filtro and not a drain field? One reason is because the filtro does not use plastics. Another is that this method takes up less space, which is a requirement in colonial urban zones.
But the filtro is the hurdle, so to speak, on the toilet paper trail. Even if much of the paper discarded in a Mexican toilet remains in the fosa septica’s sediment chamber, tiny bits do float past the clarifying chamber and into the filtro, so that over time a paper mache sludge builds up.
How much time does it take to clog a filtro? Nobody knows. It depends on how big the fosa septica and filtro are, how many people are using the toiliet and how much paper or other non-biodegradable stuff they’re flushing down there. It could take three years, or five, or ten. If you don’t flush any paper, it could take fifty or more.
As you probably know, all septic tank systems eventually fill up with sludge and non-biodegradable stuff and have to be pumped out. In Gringolandia, where most septic tanks are located under a lawn in the yard, this is not such a big deal: just dig for a few minutes, screw off the lid and pump away.
In Mexico, maintenance can be a bit more trouble. Many fosa septica are located under the patio, or they might be under the foundation of your house or even partially under your neighbor’s house, because many of these old colonial homes are the result of subdividing a larger mansion. Even when located in a back yard, the access is limited, which means the workers and their hoses will probably be coming through your front door. What’s more, most fosa septica are as old as the houses. Digging into them, like unearthing an ancient tomb, can be risky, leading to cracks or a complete collapse.
This is where famous Mexican thriftiness meets Mexican toilet training. No matter what their socio-economic station in life, Mexicans stretch their pesos and pretty much everything else. When the convenience of flushing paper down the toilet is at the expense of flushing pesos by cracking open a fosa septica, Mexicans would rather have the pesos. In this sense, it would be as rude to flush paper down your host’s toilet in Mexico as it would be to leave the door open on their refrigerator.
Most new homes and residential developments being built in Mexico today do use plastic septic tanks in their construction. When we were working on the design of our new home, we were offered the choice of a plastic septic tank or the traditional fosa septica. The plastic version, called a Septi-K, is billed as an environment-friendly version. It costs less than a fosa septica and has a cover you can remove to rinse the internal filter. The clarified liquids empty into a leach field or French drain. Every ten to 30 months, depending on use, you have to manually remove the lodo (uh... mud), which you can put in your yard as fertilizer or perhaps share with friends. And you can flush paper into it like a gringo.
Hmmm…
When we visit Gringolandia, we now feel uncomfortable putting paper in the toilet. Is it because sorting recyclables by hand is planet-friendly? Is it because it feels like throwing money down the toilet? Or is it just force of habit? Hard to say. In the end, we chose the traditional fosa septica for our new house.
So now you know what to do when you visit our bathroom and why you are doing it. Thanks to you, we may never have to service our fosa septica. At least in this one small way, we have assimilated into Mexican culture.
Comments
Kim 17 years ago
To writer and repliers...
All very informative and I must say, amusing too! I've never seen such an in-depth discussion about the disposal of toilet paper and its effects -- period.
While relatively new to the Yucatan, I definitely learned something worthwhile!
I hope Al comes out to look at the system!
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athena 17 years ago
waw thanks! now i know where flushed toilet papers go..
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Michelle 17 years ago
I live in a latino neighborhood in Washington state USA. My son is 6 years old and has tons of little friends in and out all day. It was so frustrating to me to find "poopy" toilet paper in my waste basket in the bathroon. I couldn't figure out why the heck they don't flush the paper!?! I was a bit disgusted the first time it happened and thought it was an anomaly (an odd duck who's family had funky plumbing) but friend after friend that does his business in my home deposits the paper in the 'basura' instead of flushing it. Thank you Google and Yuchatan Survivor for answering this riddle!! I knew I'd find an answer somewhere and now that I understand from where this phenomenon comes, it's not a big deal.
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Frances from Cuernavaca 18 years ago
Hi all!
Writer and repliers. What an interesting article and great answers (most). I live in Cuernavaca and have lived in Mexico for 5o years and can agree with anecdotes and discussions on throwing away the paper or flushing it. I have had a fosa septica up chuck and it was a mess. It took me years to find out what the problem had been and probably still is. Supposedly the bacteria clean up and process the residues yes but....that is if you don't have chlorine freaks cleaning your house and using gallons of the stuff not only on / in toillets but on everything else!!! Cholrine or Clarasol seems to upset the bacterial ecosystem killing the good guys that do the natural composting. Now we have non chlorine substitutes available but still, it is a popular belief that there is nothing like chlorine to disinfect -- EVERYTHING --. I will be building my home soon and I just looked up "fosa septica" out of curiosity to find out where it should be (Feng Shui would not have in the area of love for example) and chanced upon this page. It has been good reading and very illustrating. Yes Yucatan has its very particular geographic quirks, so I have learned some new things too. This wc wastebasket thing we have is a great incentive for creative arts and crafts. We must have some of the corniest and Kitchiest super decorated WC baskets in the world!.
Saludos, from the city of eternal spring and perpetual pot holes
Frances GZ
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Al 18 years ago
I'm a civil engineer and have worked on water & waste water systems for 28 years. Will be in Merida, Jan 18th for 2 weeks. I'll design you a system for free that will take toilet paper if you get in touch with me.
1st of all--you need to put in a tank that will handle your flow--too small and incoming flows flush out the solids; need a tank with baffles and a outlet pipe that is several feet below the water level so that solids can NOT leave the tank & block the drain field. You should have a drain field but here in PA, lots of homes on limestone just drill a shallow well, drop in a stick of dynamite to fracture the limestone and send their waste water from the tank into that hole.
Biggest thing is maintenence which hardly any one does. Tanks hold solids but not forever--must be pumped every 3 or 4 years. Some communities up here now mandate pumping and local building inspector checks every so often.
If drain field is blocked with solids such as bits of toilet paper, use plumber grade sodiom hydroxide to dissolve all solids--not stuff they sell to home owners--plumber grade!
Do NOT build a drain field using limestone screenings as your "sand" Chemicals flushed into system will turn your limestone "sand" into concrete eventually.
Staying at Hotel Mucuy after Jan 19th--look me up if you have any questions about your system.
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SBRodrigues 18 years ago
Thanks for the informative article, and long array of comments. I grew up close to the Mexican border and have followed the "when in Mexico" tradition there and on trips to Cuba, but now feel better prepared to explain why. We're also beginning to build a home in the Yucatan and this will be helpful.
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Denis Larsen 18 years ago
What a wonderful discussion thread! For most of the past 40 years I have lived in suburban New Jersey and used a septic system with no problems. We flushed toilet paper. However, as a precaution, every two or three years we had the system pumped out and never experienced any problems even with clothes washer and dish washer draining into the same tank. My land beneath my house was was pure sand for at least 20 feet so there was no issue of drainage.
I'm still in process of reconstructing an older home in Valladolid and had the workmen break the seal on the access panel on the fosa septica to pump out the tank. To my great surprise, there were two chambers seperated by a concrete block wall...part for solids, part for liquids. I had expected a powerful odor upon opening the tank, but there was no smell at all. And the levels of the tanks suggested that natural agents had been working very efficiently for many years. The workmen I hired to clean the tank said that there was no need to do so...so they lost out on a job and were only paid for inspecting the tank.
It probably also helps that the entire septic tank looks as if it might be a natural "cave" that has been tuck-pointed here and there on the walls with bits of stone and motar. If it had not been used as a septic system for years, I would make it into a wine cellar or a bomb shelter or a root cellar...or maybe a huge hot tub. It's as big as most of the houses in the villages of the Yucatán!
In many area of Mexico, I have noticed the odor of human waste in almost any area that I have been in. An that is because of the registros (the water traps) that Miguel mentioned above. They are in fact mini septic tanks that are placed along the waste line. Liquids and solids flow through PVC pipes into the concrete block tanks where the solids tend to stop and stay while the liquids exit through another PVC pipe. I believe these traps are the source of the very common odor of sh*t that one encounters throughout Mexico (and the rest of Latin America). When you start looking, these registros seem to be everywhere in urban areas. Each of these registros also has a removable panel for cleaning. They system works fine.
When we were constructing the waste lines for the house (whilch will be a 10 bedroom/13 toilet bed and breakfast, by the way), I attempted to persuade the plumber to just install PVC cleanout traps instead of building the registros. But he would have none of it. He was sure that they wouldn't work as well. And since I am learning, little by little, that I, as yet, do not know it all, we did it the Mexican way and not the gringo way.
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John Calypso 18 years ago
In our part of Mexico (Xico, Veracruz) most of the toilets simply dump into the otherwise clean rios - TOTAL insanitity!
Even though EVERYONE in our Colonia, gringo or Latino, does this we choose to use a compost toilet that quite simply works very well AND it certainly is nicer to use than the little baskets for toilet paper.
I have an Ebook titled Human Manure that I will email to anyone that sends me email asking.
Please think about the general lunacy of fouling clean water with human waste at any level of society(ties).
John Calypso
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Roving Gastronome: The Blog » Blog Archive » Best. City. Ever. 18 years ago
[...] Not only had I just read all about the complexities of Mexican septic systems on their site, but I just came home tonight and saw they’ve got a whole post on the Bici-Ruta program, with pictures (dig that last guy’s ride!). To get an idea of the scale of the shut-down, imagine if Broadway in Manhattan were closed to car traffic between, say, 72nd Street and Union Square. Dreamy. [...]
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Working Gringos 18 years ago
Ray,
The architects and engineers we've talk with about this subject say that the limestone shelf under our feet in Yucatan is a pretty effective filtration system. Where we lived in California, near the coast, the only thing between the septic tanks and the water table was about 10 meters of sand!
We also suspect that engineering standards and practices have changed a bit since Miguel built his house (see comments, above). That said, there are places around Merida where a cenote or underground river can be much closer to the surface than the average 25 to 40 meters.
Meanwhile, as of today, this article is the most read article on this website. What does that say about our readers?!
Wait, don't answer that...
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Ray 18 years ago
Just wondering if anyone knows what the filtration properties are of the limstone and other minerals and soil in the Merida and Yucatan region. My reason for asking is in response to the issue raised by in one of the comments about polluting the underground rivers, etc.
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