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
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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Working Gringos 18 years ago
Dear Mr. Dery,
Here's a link to a step-by-step process (in Spanish) for making a low-cost fosa septica that has been distributed to Mayans on the Yucatan Peninsula. It was produced by the University of Quintana Roo with support from the University of Rhode Island and funding from USAID. Maybe it will be helpful:
Pasos para Construir tu Propia Fosa Séptica (PDF Format)
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Danielle Dery 18 years ago
Oh! Miguel how interesting are your comments!!
I am a biologist/ecologist from Quebec province, Canada and even with all the good possibilities or modern technology we have for disposal of s**t and toilet paper, i can tell you, I was born (1956) in the country, not in a big city, and all my life we did use a garbage trashcan for our pieces of toilet paper or kleenex in our bathrooms at home or at our country cottage, this was too close to the lake! We considered it pollution!
In the time of my parents and grand-parents on a side of the farmhouse there was a simple hole in the soil with a wood door on top, no more. They would empty it by hand with shovels and use it in their fields and gardens as bio-compost.
** Funny fact or coincidence when i found this website about septic tanks: i met a friend this week on the internet looking for a very simple, cheap, easy to make and function: "ecological toilets" and sewer systems to build asap all over little villages of Peru!... especially in poor areas or villages in the mountains, far away and difficult to reach.
** Your sugestions are really Welcome to: dery1956@yahoo.ca
Thank you! Muchas gracias amigas-gos!
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Miguel Cerón 18 years ago
I enjoyed reading your article. It is nice to know someone else has thought about this subject and given an explanation so people can understand. I have thought about the subject too, and I would like to add some comments.
I was born in Yucatan but my wife is from Iowa. When we built our house in Mérida, I did everything I could to have an "American" house for her. We installed a high pressured water tank with a pump that keeps high presure in the house, special copper pipes for the running water and 4 inch pvc pipes for the drain. I also studied the differences between the plastic septic tanks and the traditional concrete ones. My main intention was precisely to avoid the waste basket for the toilet paper. I wanted to throw the paper in the toilet as they do in the USA.
I did not use the plastic septic tank because:
1 ) The largest one is very small and if you add "modules" to it then it becomes very expensive.
2 ) If you bury the tank there is a good chance it will collapse, so most engineers will advise you to make a chamber for it. The chamber needs cement walls and floor as well as a concrete top with cement lids on top of the plastic easy-off lids.
3 ) You will still not be able to throw the paper down the toilet because depending how far the septic tank is from your bathrooms, the local construction codes demand water traps every so many meters. This traps defeat the plastic tank eficiency to deal with the paper because it acumulates on the walls of the trap and starts catching anything going by. The traps slow down the water presure so the toilet does not flush down hard, instead the water stops along the way, overflows and goes on to the next trap until it gets to the septic tank.
I requested for my house to have the PVC pipes going streight down in an angle to the pit, even suggested small PVC traps to control the odors, but no local architect, engineer or contractor even tryed to find a solution. I explained to the contractor that i wanted to place the toilet paper in the toilet but he said it will cause problems in the long run no matter what.
More concerning than the toilet paper going down the drain is the fact that Mérida, an 800,000 people city, has no sewage system or waste water treatment plants. Back in the 60's the city made an attempt to equip the city with a sewage system. Due to the extremly hard rock the peninsula is made of, digging takes a little more than a shovel. A company by the name of caterpilar designed a trencher special ordered for the project. The machine was able to make a trench trhough Colonia Aleman but it broke so many times that the Caterpilar people gave up. Today the only urban area equiped with a sewage system is Colonia Aleman. Where does the sewage go? Who knows? I think it ends by Pinos which was uninhabited back then. There is no treatment plant so it must go down into the ground. Today there are machines that can break the Yucatecan rock but the problem and the project is so big no governor or city major wants to even mention it. All the septic tanks down town do not comply with regulation and probably 70% of the urban area septic tanks are not well done either. All that waste is going down into the underground water system that naturaly supplies the peninsula with the precious liquid. Yucatan does not have any other water sourse (rivers, lakes) but the rain. Once we polute the underground reserves, we will be in big trouble.
The city keeps growing and the big construction corporations still get away with cheap septic tanks. Even today's Altabrisa with hospitals and hotels that will produce tons of waste are not required to treat the waste water.
If this enourmous projects were being build in Sian Kaan or Celestun, they would be required to finance a waste treatment plant to protect the Iguanas or the flamingos. However since they are beeing built in Mérida it is okay for them to pollute the environment, after all it is only humans living around them.
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bob 18 years ago
Very interesting especially the replys
please keep up sending these letters.
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Working Gringos 18 years ago
WGringa just came back from a short trip in California and noticed that the majority of public toilets now seem to have wastebaskets next to them.
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JEFF 18 years ago
THIS IS WHY ONE MAY FIND PAPER ON THE GROUND IN HISPANIC POPULATED AREAS IN CALIF
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Kati 18 years ago
Very interesting. I live in the country and while I don't know how old the septic system is in the old farmhouse I am renting, over the last two years, we have noticed the leach field is blocked -- here, probably by tree roots which are trying to take back the meadow...The job of digging up the old system and/or replacing it with new hasn't begun yet; I don't envy my landlords of that bill when it comes in.
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Mike 18 years ago
I believe other things play into the toilet paper waste basket mystery. I Live in the US and commute daily to Mexico for work. Prior to this I lived in Mexico for 8 years. I have noticed in this time that my friends and family south of the border including our family in Merida use waste baskets. Many bathrooms I have visited seem to need maintenance on the toilets. Because of poor water pressure and water quality, the inners of a toilet need more attention. I find that the tanks do not fill up enough on the toilet to flush properly. It barely flushes the human droppings. Also in many older homes, The pipes from the toilet to the septic are not laid out efficiently, therefore they clog faster. I think if people would maintain the "whole" waste system including water delivery, The security of flushing paper would have a new mentality.
MM
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Working Gringos 18 years ago
Kim,
Perhaps the article wasn't emphatic enough. Drain fields don't clog. Filters do. Nearly all of the paper that remains in the sediment chamber does in fact get broken down by bacteria. But bits of paper float through the septic tank and into the drain field or the filter pretty much right away. Drain fields don't clog because there are holes all around the pipes, top and bottom, and gravel around that, spread out over a relatively long distance. But filters of any kind do clog: oil, air, septic, etc. You have to clean or replace them, even in modern systems, like the one shown above.
Most of the non-biodegradable stuff you mention is embedded in heavier, uh, stuff, and not floating free like paper, so it stays in the sediment chamber. Anyway, that's the short answer. There are several other factors covered in the article, including maintenance issues if something does go wrong and cultural biases, and others that are not covered, like how robust the bacteria are. You could write a master's thesis on sewage treatment, and many have.
Although every provider of septic tanks recommends a pumping schedule, you can't predict with certainty when maintenance is required. You just have to check, which is not a particularly pleasant option with the old fosa septicas here.
Meanwhile, we are quite convinced that many colonial-era fosa septica in Mexico have been functioning for over fifty years or more.
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Kim Galle 18 years ago
Having grown up in country in Northern CA where we flushed toilet paper for years into our septic tank, I still find the above puzzling. We had a tank which worked as described above, with a drain field, and during my entire youth (18 yrs or so) it was never pumped once, and never gave signs of malfunctioning, stoppage, etc. And it seems to me that toilet paper, being basically organic itself, should also be eaten by the bacteria, leaving very little cellulose behind. Certainly what we eat (think of corn, lettuce, whole grains, etc) leaves behind at least as much cellulose as paper. And even cellulose should be eaten by bacteria. Just think of rotting trees in the woods.
I appreciate the article (also that on the plumbing system). But I think it still raises as many questions as it answers.
Thanks,
Kim
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