The tap water provided by the City of Houston is generally considered safe to drink and meets or exceeds all federally mandated safety standards set by the Environmental Protection Agency (EPA). Houston Public Works ensures continuous compliance with the Safe Drinking Water Act (SDWA). However, the word “safe” is defined by compliance with legal limits, and some consumers choose to use home filtration for taste or to reduce trace contaminants that fall below the regulatory threshold.
Where Houston’s Water Comes From
Houston’s water supply is sourced primarily from surface water, with approximately 86% coming from major reservoirs fed by river systems. The Trinity River and San Jacinto River systems feed into Lake Livingston, Lake Conroe, and Lake Houston, which serve as the city’s main water storage areas. The remaining 14% of the supply is drawn from deep underground wells that tap into the Evangeline and Chicot aquifers.
The city operates three surface water purification plants and numerous groundwater plants. Water is first treated through processes like coagulation and sedimentation to remove large particles and suspended solids. This is followed by filtration, which removes smaller impurities and microorganisms.
The final step is disinfection, where chemicals like chlorine or chloramine are added to kill any remaining bacteria and viruses before the water is distributed. This multi-step process ensures the water leaving the treatment plant is free of harmful pathogens and meets all state and federal standards. The use of surface water has increased over the last two decades to mitigate the effects of ground-level subsidence caused by excessive groundwater pumping.
How Water Quality Is Regulated and Reported
The safety of Houston’s drinking water is overseen by a rigorous regulatory framework involving both federal and state agencies. The U.S. Environmental Protection Agency (EPA) establishes the national standards under the Safe Drinking Water Act (SDWA), setting enforceable Maximum Contaminant Levels (MCLs) for various substances. These MCLs represent the maximum amount of a contaminant allowed in public drinking water.
The Texas Commission on Environmental Quality (TCEQ) is the state agency responsible for implementing and enforcing the EPA’s standards within Texas. The City of Houston must conduct frequent and mandated testing to ensure its water remains compliant with these standards. This compliance is monitored closely by the TCEQ, which ensures public water systems meet all required testing frequencies.
To maintain transparency, the public water system is required to publish an annual Consumer Confidence Report (CCR), also known as the Water Quality Report. This document summarizes the water sources, any detected contaminants, and compliance with all MCLs for the previous calendar year. Houston residents can access this report directly through the Houston Public Works website to review the city’s compliance data.
Addressing Specific Local Contaminants
While Houston’s water meets all federal standards, certain contaminants are routinely detected. One common issue is the presence of disinfection byproducts (DBPs), specifically Total Trihalomethanes (TTHMs) and Haloacetic Acids (HAA5). These form when the chlorine or chloramine used for disinfection reacts with naturally occurring organic matter in the surface water sources. Although the levels are kept below the EPA’s MCLs, prolonged exposure to DBPs has been associated with potential health risks.
The potential for lead contamination is another major concern, though the water leaving the treatment plant is typically lead-free. Lead enters the drinking water when it leaches from aging lead service lines, interior plumbing, and fixtures in older homes. The city is currently undertaking a comprehensive inventory of all service lines to identify and address any lead-containing pipes, as mandated by the EPA’s Lead and Copper Rule Revisions.
Houston’s water is also notably hard, meaning it contains high concentrations of dissolved calcium and magnesium minerals. While hard water is not a safety concern, it can cause mineral buildup on plumbing and appliances. Additionally, trace amounts of naturally occurring substances like arsenic and Chromium-6 are sometimes detected, originating from the region’s rock and soil composition, especially in groundwater sources.
Actionable Steps for Home Consumers
Home consumers can take simple steps to further ensure water quality. If a home has older plumbing, flushing the cold water tap for 30 seconds to two minutes before drinking or cooking reduces potential lead exposure. This action clears water that has been sitting in contact with service lines and fixtures.
For individuals seeking to improve taste or reduce trace contaminants, a home filtration system is a practical option.
Filtration Options
- Carbon-based filters, such as pitcher or faucet-mounted types, are effective at removing chlorine, chloramine, and associated taste and odor.
- More advanced options, like reverse osmosis (RO) systems, can significantly reduce heavy metals, arsenic, and disinfection byproducts from drinking water.
In the event of a localized issue, the city may issue a boil water notice. This requires residents to bring tap water to a rolling boil for at least one minute before consumption. This temporary measure eliminates harmful bacteria or pathogens that may have entered the system due to pressure loss or infrastructure failure. Residents should pay attention to local advisories and consult the annual Consumer Confidence Report to stay informed.