Potable water being delivered to a cistern in San Miguel de Allende (C) Daniel FriedmanDrinking Water San Miguel de Allende
Water contaminants, sources, treatments & Water Quantity Limitations

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This article provides information & research describing the quantity and quality of drinking water in and around San Miguel de Allende in Guanajuato, Mexico.

Notice: this document is in DRAFT form for REVIEW purposes and will require corrections and additions as it is reviewed by water quality experts. Please use the page top or bottom CONTACT link to offer suggestions, research, or additional content.

This article series explains limitations on both water quantity and water quality available and describes conditions impacting the future quantity and quality of water available in the area of San Miguel de Allende, a city in central Mexico in the state of Guanajuato. The combination of climate change, population increase, and increased water usage for agricultural or industrial uses imposes limitations that face state and local governments as well as private citizens.

This article series also explains the limitations of relying only on disinfection (chlorine or other disinfectants) to make drinking water safe and potable if / when inorganic contaminants such as arsenic, fluorides, or lead are present in water supplies of any community.

Our page top photo shows potable water being delivered by a pipa (water delivery truck) to a storage cistern in San Miguel de Allende, Guanajuato, Mexico. Many residents in Guanajuato rely on purchase of bottled water from Ciel or other purified water suppliers in the area.

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Drinking Water Quality in San Miguel de Allende, Mexico, Research, Monitoring, Test Results

Water softener installation in San Miguel de Allende (C) Daniel Friedman

Our photographs above and below show the installation of rooftop water treatment equipment on a home in San Miguel de Allende in Guanajuato, Mexico.

In a proper design the sequence of water treatment equipment is important. In the water treatment system shown here, water passes from the municipal supply piping up to a rooftop water storage tank and from the tank through a pressure booster pump, through a water softener, then through water filtration equipment, and then through a UV light disinfection system.

[Click to enlarge any image] The preparation of this Fleck water softener for use by filling the blue poly glass resin tank is described at SOFTENER RESIN REPLACEMENT.

As we mention below, one or more point of use reverse osmosis treatment systems may be used to remove inorganic contaminants not handled by the rooftop water treatment equipment.

The first photo shows a high capacity water softener (blue resin tank) along with its black brine tank (salt tank).

Water softeners are used to remove high levels of minerals, principally calcium and magnesium from the water supply, thus avoiding excessive scale formation (sarro) that blocks piping and clogs tankless water heaters as well as leaving hard-to-clean white deposits on plumbing fixtures. We illustrate the installation of this water softener at SOFTENER RESIN REPLACEMENT.

WATER SOFTENERS & CONDITIONERS - provides a complete guide to water softening equipment installation, use, maintenance.

Our second photo, given below, illustrates a typical pair of whole house water filters (those vertical blue cylinders).

Water passes first through a sediment filter and second through an activated charcoal filter.

More about these sediment and activated charcoal filters is at WATER FILTERS, HOME USE.

Above the two water filters in our second photograph you'll spot a horizontal stainless steel tube that contains a water disinfection system, a UV light.

Water filters & UV disinfection installed in San Miguel de Allende (C) Daniel FriedmanFor a UV lamp to work it is essential that it is protected from clogging by sediment or mineral scale.

For this reason, the UV light is (almost) the last step in this series of water treatment equipment for the building.

At UV ULTRAVIOLET LIGHT WATER TREATMENT we explain that UV light disinfection systems can kill bacteria but not in all forms: certain cysts are very resistant to UV disinfection.

Out of the UV lamp water passes into the building for use at various plumbing fixtures.

Do not try following the green water supply piping in these photos as it will give you a headache. On the pipes for an installation like this one we mark directional arrows to help future users understand how the system is working.

In both photographs you'll notice a black Grundfoss SCALA2 pressure booster pump necessary to send water from the rooftop water storage tank through this water treatment equipment and onwards into the building they serve.

More about methods for boosting water pressure and the Grundfoss SCALA2 variable speed pump are at WATER PRESSURE BOOSTER PUMP.

When all of this water treatment was installed and working in the building one of the installing plumbers commented

"Well now you can drink this water with no worries."

Really? Not necessarily.

Depending on where a building is located in the city, and depending on which of San Miguel de Allende's twenty water wells is supplying it, how the municipal water supply may be mixed from these source wells at different times of the year, how heavy might be the current water usage in the city, and seasonal as well as long term lowering of the water table, even a municipal water supply is at risk of encountering non-biological contaminants such as arsenic, mercury, or fluorides that would require additional steps to remove them from the water supply.

In addition to the equipment outlined above, one or more point of use (POU) reverse osmosis systems (RO) may be installed, such as at a kitchen sink, to remove inorganic contaminants that might sometimes be present in a water supply such as arsenic or fluorides. The RO system is not shown here.

Details about reverse osmosis water treatment equipment are at REVERSE OSMOSIS WATER TREATMENT.

Below we provide research and information sources that address water quality and potability questions for the greater area of San Miguel de Allende.

Watch out: most point of use water filters such as carbon filters and other "magic bullet" "water purifier filters" sold for use at a water tap or sold as pitchers that include a water filter are ineffective, unreliable, and may be downright dangerous for users as water contaminants vary over time even in a municipal water supply. Yet we see such products widely used both in private homes and in some restaurants and other public facilities.

Even ceramic water filters, generally a broadly-effective water filter and one of our favorites, are limited in their ability to remove inorganic water contaminants.

Special thanks to Dylan Terrell, Executive Director of Caminos de Agua, for providing some of the technical resources given here.

Research & Water Quality Information Sources, San Miguel de Allende & Other Areas

Water truck in Uruapan being filled from the Manantial  (C) Daniel FriedmanWater quality in Mexico is monitored by CONAGUA and is further monitored by the Secretary of Health. In addition local water quality monitoring is performed by the local water department providing water to the muncipality, such as SAPASMA. The reports of that monitoring are not easily obtained by the public, and many water supplies, both public and private, have to cope with contaminant levels that vary by season, usage, and geography.

Water quantity and quality vary widely across Mexico, geographically, seasonally, and as a feature of increasing water usage, as it does in most other countries.

The Manantial Yerba Buena, in Uruapan, Mexico, provides voluminous potable water that here is shown being loaded into a pipa.

Example of water quality test results on Caminos de Agua map,  San Miguel de Allende, Guanajuato, Mexico - at original source:

[Click to enlarge any image]

Water Quality & Water Quantity Research: San Miguel de Allende, Guanajuato, Mexico

As we discuss separately at WATER DISINFECTION LIMITATIONS, there is growing evidence that drinking water disinfection alone can be ineffective in adequately removing drinking water contaminants, both because of procedural errors and possibly because of persistent contaminant sources or contaminants that are partly-encapsulated inside water piping or containers, requiring extra contact time or additional cleaning and disinfection methods to assure a stable sanitary drinking water supply.

Examples of Water Disinfection Limitations

Watch out: as we report throughout this article series, different disinfection methods vary in their effectiveness in combating different types of water contaminants. If you rely on a single disinfection method, for example chlorine disinfection, your water supply could still be contaminated by cryptosporidium, or if chemical contaminants are present, those, too, might remain.

Municipal water supplies are generally safe as their water treatment efficacy is monitored regularly as required by federal regulations. But private water supplies may be at risk.

Consulting with your local health department and local water testing laboratories can provide locally-accurate advice on what water tests are most important to perform in order to understand what water treatment may be necessary for your home or building.


Continue reading at WATER DISINFECTION LIMITATIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.




Or see REVERSE OSMOSIS WATER TREATMENT - capable of removing arsenic, fluorides, lead, other contaminants, but also consuming water in the process





Or see WATER SOFTENERS & CONDITIONERS for treatment of water high in mineral content



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WATER QUALITY & QUANTITY San Miguel de Allende at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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