The Mexican House Water System Explained Living Mexico

The Mexican House Water System Explained

There is no doubt you’ve seen them. The (usually) black tanks on top of nearly every house in the country. Welcome to the Mexican water system. The black Rotoplas tanks, which are also cream colored, is the water source for your home.

There was a time when water was only available during certain hours of the day in certain neighborhoods (although that has changed over the years, I currently live in a neighborhood that still has scheduled city water flow). When your house (your neighborhood) was not receiving city water, you used the tank on your roof. If you ran out, you’d have to wait until it was your neighborhood’s turn again.

When I lived in Cancun I had a small house in the city’s center. It was the oldest part of Cancun making it an original area where city water ran through the pipes only during certain times. In my neighborhood (which was SM4), water was available to refill the tanks from 8:00 p.m. until 3:00 a.m.

You’ve probably already done the math to realize how incredibly inconvenient that is. Think a shower, a few toilet flushes and a single load of laundry and, you guessed it, the tank would be empty until 8:00 p.m. It is for this reason you’ll also see a lot of Rotoplas tanks on the ground (cistern) or a second one on the roof (tinanco). The cisterns are extra water reserves for your tinanco and, with the addition of an electric pump that sits at its base, refill your house water tank in between city water fills.

The tinacos are up high because they act on natural water pressure. The higher the tank, the more natural water pressure. Most of us have also added an extra line or two (3/4″ white plastic water line that is placed vertically and spliced into your main water lines) to add air flow into the lines and help increase pressure.

This is the old, but very efficient and inexpensive way to gain water pressure in your house. To receive water from the city line to your tinaco, we all rely on city pumps. When we have power outages, no electricity means no functioning pumps, which means no water being pushed through city lines.

On the other hand, when we have power outages, we all have a tinanco, so during storms for example, we can get by until the city fixes things. So there is a good side and a down side to the system. As a single woman, I can make my 450-liter tinaco last as long as four days if careful.

A lot of people add small half-horsepower water pumps at ground level to help pump water from the main city line up to their tank. This is only necessary if you live you in area where there are known (and frequent) main city pump issues.

These added pumps have nothing to do with the water pressure inside the home, however, you can buy special pressurizers that go against the tinaco to add water pressure to the main lines. This method will also increase your water bill usage by at least three times the amount each month.

The Mexican House Water System Explained

The water tank refills in the exact same concept as the back of your toilet. When the floater and arm go down, water flows in. When the floater is up, the water shuts off.

I’ve done years and years of my own water tank maintenance and think it’s a good idea for everyone to learn, because due to the hard water here, it’s inevitable you’ll need to replace the parts at least once a year.

How do you know when it’s time to replace the parts? You will have one of two experiences:

  • You’ll be in the middle of something water-related and discover your tank is empty and not receiving more water (even though the city water source is flowing) OR (my personal favorite)
  • During the night when you’re enjoying the most sound sleep, you’ll suddenly hear water running down the side of your house like no-one’s business. You can lay there and hope the problem belongs to your neighbor (been there done that), but it rarely does.


To solve that middle-of-the-night problem, simply run outside and turn off your city water supply. The water flow to your tank will be cut and, once the level in your tinaco balances out, the overflow will also stop.

You can then deal with it in the morning. To fix it:

You can wait for “a guy”, who will likely show up in a day or so, or you can just scoot down to your local ferreteria and grab a new floater set (sold in a complete package for under 120 peso) and install it yourself.

What tends to happen is simple: the hard water builds up and either affects the balance ability of your floater or the arm becomes coated with hard water and gets stuck (either in the up or down position). It’s not the end of the world and is an easy, inexpensive fix.

As a note, it is imperative that you return the lid to your tank and make sure it’s secure. They do tend to blow off (not often, but it happens) and while you can easily buy a replacement lid for around 250 peso, the water in your tank and lines to your house will go rank within a month or two of no top. Unless you’re on your roof on a regular basis, it will take you that long to notice the top is missing and the cleaning bill for that is not cheap.

It doesn’t take long to change the floater and arm on your water tank, only about as long it would to change had it been your toilet that needed the repair. It’s super-easy and is part of living in Mexico.

Love, Roaming Canadian