San Antonio Water Quality Report 2026: What’s in Your Tap Water

QUICK SUMMARY:

Overall Rating: Fair
Top Contaminants of Concern: Very hard water from the Edwards Aquifer (15–20 grains per gallon), and disinfection byproducts — total trihalomethanes (TTHMs) and haloacetic acids — that form when free chlorine reacts with the natural organic and bromide content of the source water
Recommended Filter Type: A whole-house softener for the hardness, paired with carbon filtration or reverse osmosis at the kitchen tap for the disinfection byproducts — see the hard water guide and solutions, best under sink water filters, and best reverse osmosis systems guides
Water Hardness: Very hard — roughly 15 to 20 grains per gallon (about 257–342 ppm as calcium carbonate)

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San Antonio Water System (SAWS) serves roughly 1.8 million people across Bexar County, drawing most of its supply from the Edwards Aquifer. According to the utility’s 2026 Water Quality Report, covering data sampled in 2025, the main system recorded no health-based violations of federal standards. That statement is accurate, and it is also incomplete. Federal compliance is a legal threshold, not a measure of how clean or how pleasant the water is.

Here’s what the data actually shows. San Antonio’s tap water is genuinely strong on the contaminants people fear most — lead at the system level is very low, PFAS detections sit far below the new federal limits, and nitrate is barely measurable. The two issues worth attention are different in kind. One is an aesthetic and household nuisance that the geology guarantees: the water is very hard. The other is a health-based concern that sits close to a federal ceiling: the byproducts of disinfecting that water. The distinction matters, because the filtration that solves one does little for the other.

Where Does San Antonio Get Its Water?

San Antonio is, unusually for a major US city, a predominantly groundwater system. The Edwards Aquifer — a vast, fast-recharging limestone formation beneath the region — supplies the majority of SAWS water. The utility supplements that source with the Carrizo and Trinity aquifers, recycled and stored aquifer water through its Aquifer Storage and Recovery program, and the Vista Ridge regional pipeline. SAWS also operates a brackish groundwater desalination plant in southern Bexar County, the largest inland desalination facility of its kind in the country.

The defining fact about this supply is the rock it moves through. The Edwards Aquifer is limestone — calcium carbonate — and water sitting in and flowing through limestone dissolves a large amount of that mineral. The result is water that arrives at the treatment plant already very hard. Limestone aquifers also tend to carry elevated bromide, a naturally occurring ion that has no direct health limit of its own but plays a quiet role in the disinfection byproduct chemistry discussed below.

How San Antonio Disinfects: Free Chlorine

SAWS disinfects the main San Antonio system with free chlorine — not chloramine. This is worth stating plainly, because several aggregator and water-treatment vendor pages claim the city chloraminates, and that claim is not supported by the utility’s own documents. SAWS’s water quality FAQ states that “chlorine is added to public drinking water to keep the water free of bacteria,” and the 2026 Water Quality Report lists the residual disinfectant as “Chlorine Residual, Free,” averaging 1.46 ppm against a federal maximum of 4 ppm.

That choice has a direct consequence for your filter. Free chlorine is removed readily by ordinary activated carbon (a porous carbon media that adsorbs chlorine and many organic compounds). You do not need the catalytic carbon that a chloraminated city would require. The trade-off built into free-chlorine disinfection appears downstream: free chlorine reacts more readily with natural organic matter to form regulated disinfection byproducts than chloramine does, which is part of why San Antonio’s byproduct numbers sit where they do. For the difference between the two disinfectants and how each behaves at the tap, see our guide to chloramine vs chlorine in tap water.

What Contaminants Are in San Antonio Tap Water?

The table below draws on SAWS’s 2026 Water Quality Report (data sampled in 2025, with a few parameters carried from 2023–2024 monitoring cycles) and the EWG Tap Water Database. One column needs explaining first. The EPA’s Maximum Contaminant Level (MCL) is the legal limit — the number a utility cannot exceed without a violation. The EWG Health Guideline is a stricter, health-based benchmark set at a one-in-one-million lifetime cancer risk. The gap between the two is where most of the meaningful risk lives, because the federal legal limits for the disinfection byproducts have not been updated in close to two decades.

Contaminant	Detected Level	EPA MCL	EWG Guideline	Health Concern
Total trihalomethanes (TTHMs)	86.2 ppb (highest locational annual avg)	80 ppb	0.15 ppb	Cancer, fetal development
Haloacetic acids (HAA5)	30.6 ppb (highest locational annual avg)	60 ppb	0.1 ppb	Cancer, reproductive harm
Dibromochloromethane	Up to 9.9 ppb	(part of TTHM)	—	Cancer
Lead	1.6 ppb (90th percentile)	15 ppb (action level)	0 ppb	Neurological damage
Copper	0.187 ppm (90th percentile)	1.3 ppm (action level)	—	Liver, kidney
Nitrate (as N)	2.45 ppm	10 ppm	0.14 ppm	Oxygen delivery in infants
Uranium	1.7 µg/L	30 µg/L	—	Kidney toxicity, cancer
Radium (226 + 228)	1.5 pCi/L	5 pCi/L	0.05 pCi/L	Cancer
Fluoride	Below 0.69 ppm	4 ppm	—	Dental health at trace levels
PFOA / PFOS	Not detected above reporting level	4 ppt each	0.09 / 0.3 ppt	Cancer, immune effects

Read the trihalomethanes row carefully, because the nuance is the point. The 86.2 ppb figure is the highest locational running annual average recorded across the distribution system in 2025. The federal standard is assessed as a system-wide running annual average, and on that basis SAWS reported no TTHM violation. Both facts are true at once: the system passed, and at least one corner of it ran above the 80 ppb legal ceiling on an annual-average basis. Other monitoring zones in the same report came in lower — 71.3 ppb and 53.9 ppb among them. Measured against the EWG health guideline of 0.15 ppb, even the lower zones sit hundreds of times above the health-based benchmark. That is precisely where regulators and consumers tend to talk past each other.

The disinfection byproducts deserve the most attention of anything in the table, for two reasons. They sit at the highest fraction of their legal limits of any health-based contaminant here — TTHMs at or slightly above the MCL at the worst-case location, HAA5 around half the MCL. And the health endpoint, increased lifetime cancer risk with some evidence of harm to fetal development, is well characterized in the research. These compounds form when free chlorine reacts with natural organic matter in the source water. San Antonio’s groundwater also carries elevated bromide, which pushes the chemistry toward brominated byproducts — the report’s dibromochloromethane result, as high as 9.9 ppb, is the visible signature of that bromide. They are a feature of the disinfection chemistry, not an industrial spill, which is why they appear in essentially every chlorinated system and why they are the contaminant most worth filtering here.

Several contaminants are worth singling out for being low. Lead at the system level measured 1.6 ppb at the 90th percentile in the most recent monitoring, roughly a tenth of the 15 ppb action level — and an improvement over earlier reporting cycles. The naturally occurring radionuclides that the limestone geology might raise are present but modest: uranium at 1.7 µg/L against a 30 µg/L limit, combined radium at 1.5 pCi/L against a 5 pCi/L limit. Nitrate sits at roughly a quarter of its limit. PFAS is the other good-news finding: federal UCMR5 monitoring detected only short-chain compounds (PFBS near 3.8 ppt and PFBA near 7.5 ppt) at trace levels, with the regulated PFOA and PFOS not detected above the reporting level. That is a clean PFAS result for a system this large. For households that still want a margin of safety, our best water filters for PFAS removal guide covers the certified options.

You can review the full contaminant list for your system at the EWG Tap Water Database entry for San Antonio Water System.

The Lead Question in San Antonio

Lead deserves its own note because it behaves differently from everything else above. The contaminants in the table either arrive at the treatment plant or form during treatment. Lead does not — it enters water after treatment, by leaching from lead service lines, lead solder, and brass fixtures inside older buildings. The water leaving SAWS facilities is essentially lead-free; what matters is the plumbing between the water main and your glass.

San Antonio’s system-wide 90th-percentile lead result was 1.6 ppb in the most recent sampling, well under the 15 ppb federal action level, with no sites exceeding it. But a citywide percentile cannot tell you what is happening at your specific tap, and for lead, the tap is the only measurement that counts. The use of lead materials in new service lines was prohibited in 1989, and lead solder remained legal until 1986, so the risk concentrates in older homes. SAWS now maintains a public lead service line inventory and runs a replacement program, and it advises flushing your tap for 30 seconds to two minutes before drawing water for drinking or cooking if you are concerned. If your home was built before the late 1980s, testing your own water is the only way to know your exposure. Our lead in drinking water guide covers sources, risks, and certified removal in detail.

San Antonio Water Hardness

This is the headline. San Antonio has some of the hardest tap water of any major US city, and unlike the disinfection byproducts, the hardness is not a subtle, sub-limit concern — it is something residents see on every fixture. SAWS’s own water quality FAQ reports typical hardness running from 15 to 20 grains per gallon (GPG), which corresponds to roughly 257 to 342 ppm as calcium carbonate. On the standard scale, anything above 10.5 GPG is “very hard,” so San Antonio sits well into that category.

The cause is the Edwards Aquifer. As groundwater moves through limestone, it dissolves calcium carbonate, and the resulting mineral load is what makes the water hard. There is no health concern here — hard water is not harmful to drink, and the dissolved calcium and magnesium are the same minerals found in many bottled mineral waters. The problem is practical. At 15 to 20 GPG, scale builds quickly on faucets, showerheads, glassware, and inside water heaters and appliances; soap and detergent lather poorly; and the lifespan of water-using appliances shortens measurably.

This is the one San Antonio issue where a whole-house water softener is genuinely worth considering for most households, not a marginal upgrade. Our hard water guide and solutions explains how softeners work, the salt-free alternatives and what they actually do, and how to size a system for water this hard. The key planning point for San Antonio residents is to treat hardness and disinfection byproducts as two separate jobs: a softener addresses the scale, but it does not remove TTHMs, so most homes will want carbon or reverse osmosis filtration at the drinking tap in addition.

Best Water Filters for San Antonio Residents

San Antonio’s profile points to a clear priority order: soften the very hard water for the whole house, then reduce disinfection byproducts and any plumbing-derived lead at the drinking tap. The options below are matched to that profile rather than pulled from a default list. Each carries third-party certification to a specific NSF/ANSI standard from an accredited body — verify the exact model in the certifier’s database before buying, since certification is listed by model, not by brand, and the three legitimate certifiers (NSF International, WQA Gold Seal, and IAPMO R&T) maintain separate databases.

Whole House: Water Softener (the hardness fix)

For water at 15 to 20 grains per gallon, a whole-house ion-exchange softener is the appropriate technology, and it is the single most impactful purchase most San Antonio homes can make. A softener does one job well — it replaces the calcium and magnesium that cause scale with sodium (or potassium) through ion exchange — and it is the only technology that protects every fixture and appliance in the house at once. Because the relevant certification here is for material safety and structural integrity rather than contaminant removal, look for components certified to NSF/ANSI 44 (the cation-exchange softener standard) or NSF/ANSI 372 for lead-free materials, and size the resin capacity to San Antonio’s hardness so the unit is not regenerating constantly. A softener does not remove disinfection byproducts, chlorine taste, or lead, which is why it pairs with, rather than replaces, a drinking-water filter. For sizing, salt-free alternatives, and what to look for, see our hard water guide and solutions.

Reverse Osmosis: Waterdrop G3P800 (the broadest drinking-tap fix)

Reverse osmosis is the strongest single answer to San Antonio’s drinking-water concerns, because the semipermeable membrane reduces disinfection byproducts, the brominated compounds the bromide produces, lead from household plumbing, and the trace radionuclides from the limestone — all in one system. The Waterdrop G3P800 is NSF International certified to Standards 58, 42, 53, and 372, covering reverse osmosis performance (Standard 58, including total dissolved solids reduction), chlorine taste and odor (42), a range of health-effects contaminants (53), and lead-free materials (372). Its tankless design fits under a standard sink. In a hard-water city, one practical note matters: feeding an RO unit pre-softened water meaningfully extends membrane life, so an RO system downstream of a whole-house softener is the ideal pairing here.

The trade-offs are inherent to the technology, not flaws in this model. Reverse osmosis strips minerals along with contaminants, so the water tastes flat to some people; it sends a portion of feed water to the drain; and it needs an electrical outlet under the sink. One installation note: connect the drain and feed line with compression fittings rather than a self-piercing saddle valve, which a growing number of local plumbing codes discourage because of long-term leak risk. Consumer Reports’ testing consistently ranks reverse osmosis highest for breadth of contaminant removal, which is the reason to accept those trade-offs. For comparisons, see our best reverse osmosis systems guide.

Buy Direct from Waterdrop | Check on Amazon

Under Sink (no RO): Aquasana Claryum 3-Stage Max Flow

For households that want strong disinfection-byproduct and lead reduction at the tap without RO’s drain water and flat taste, a carbon-block under-sink system is the practical alternative. The Aquasana Claryum 3-Stage is certified by the Water Quality Association (WQA), an accredited body that certifies to the NSF/ANSI standards, to Standards 42, 53, and 401 — covering chlorine taste and odor, lead, and a category of organic compounds that includes the precursors and byproducts of disinfection. Because San Antonio disinfects with free chlorine rather than chloramine, ordinary carbon block is well-matched to the chlorine and the byproducts here; you do not need a specialized chloramine unit. The Standard 53 lead certification covers the contaminant most likely to enter water inside an older San Antonio home. Note the certifier carefully: this is a WQA Gold Seal certification, so the product will not appear in NSF International’s own database — that is expected, not a red flag.

Two real limitations. First, carbon does not soften water or reduce radionuclides, so it does nothing for San Antonio’s defining hardness problem and is not the unit to choose if uranium or radium is your priority. Second, the cartridges are rated for roughly 800 gallons or about six months, and replacements cost more per gallon than a basic carbon filter — budget for that recurring cost, which in very hard water can also mean more frequent sediment pre-filter changes. For other point-of-use options, see our best under sink water filters guide.

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How to Test Your San Antonio Tap Water

SAWS’s annual report is a system-wide summary measured at the treatment plant and across the distribution network. It is the right tool for understanding the source water, and the wrong tool for understanding your specific tap — especially for lead, which forms inside your own plumbing and varies sharply from one address to the next, and for hardness, which can differ slightly depending on which aquifer source is serving your part of the system at a given time.

A certified home test closes that gap. For a broad screen, Tap Score (run by SimpleLab) sends samples to accredited laboratories and returns results you can read against the same EPA and health benchmarks used above, including a hardness measurement specific to your tap. If you live in a home built before the late 1980s, a lead-specific test is the single most useful measurement you can take. Our how to test your water at home guide explains the options and what the results mean.

Get a Tap Score Test

Frequently Asked Questions

Is San Antonio tap water safe to drink?

San Antonio tap water meets current EPA drinking water standards, and SAWS reported no health-based violations in its 2026 report. Lead at the system level is very low, and PFOA and PFOS were not detected above the reporting level. “Compliant” is not the same as “ideal,” though — disinfection byproducts run high, with the worst-case location’s annual-average trihalomethanes at or slightly above the federal limit, and the water is very hard. Both are worth addressing with the right filter, but neither makes the water unsafe by federal standards.

Does San Antonio water have PFAS?

Barely. Federal UCMR5 monitoring of the SAWS system detected only short-chain PFAS compounds at trace levels — PFBS near 3.8 parts per trillion and PFBA near 7.5 parts per trillion — while the two regulated compounds, PFOA and PFOS, were not detected above the laboratory reporting level. All results sit below the EPA’s 4 parts-per-trillion limits for the regulated compounds. For a system drawing mostly on protected aquifer water, this is a clean PFAS result.

How hard is San Antonio water?

Very hard. SAWS reports typical hardness of 15 to 20 grains per gallon, roughly 257 to 342 ppm as calcium carbonate, because the Edwards Aquifer is limestone and the water dissolves calcium carbonate as it moves through the rock. That places San Antonio well into the “very hard” category. Hard water is not a health risk, but at this level it scales fixtures and appliances quickly, which is why a whole-house softener is genuinely worth considering for most homes.

Do I need a water filter in San Antonio?

For most homes, the answer is two-part. A whole-house softener addresses the city’s defining hardness problem and protects appliances. Separately, a reverse osmosis system certified to NSF/ANSI 58, or a carbon-block under-sink filter certified to NSF/ANSI 42 and 53, addresses the disinfection byproducts and any lead from older plumbing at the drinking tap. Because San Antonio uses free chlorine rather than chloramine, standard activated carbon is sufficient — no specialized chloramine filter is required.

Sources Cited

EWG Tap Water Database — San Antonio Water System (PWSID TX0150018): https://www.ewg.org/tapwater/system.php?pws=TX0150018
San Antonio Water System, 2026 Water Quality Report (data sampled 2025): https://www.saws.org/wp-content/uploads/2026/06/2026-SAWS-Water-Quality-Report.pdf
San Antonio Water System, Water Quality Report main page: https://www.saws.org/your-water/water-quality/water-quality-report/water-quality-report-san-antonio-water-system/
San Antonio Water System, Water Quality FAQs (disinfectant and hardness): https://www.saws.org/your-water/water-quality/saws-water-quality-concerns/faqs/
San Antonio Water System, Lead and lead service line program: https://www.saws.org/lead
US EPA, National Primary Drinking Water Regulations (MCLs for trihalomethanes, haloacetic acids, lead, uranium, radium, PFAS)
US EPA, Fifth Unregulated Contaminant Monitoring Rule (UCMR5) PFAS results
USGS, Water Hardness classification scale
Consumer Reports, water filter testing

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