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TheH2O Standard

San Antonio Water System · serves 1,999,472 people

Tap Water Quality in San Antonio, TX 78205

San Antonio Water System's own testing found 15 contaminants above EWG's health guidelines, led by Haloacetic acids (HAA9) at 161x, Total trihalomethanes (TTHMs) at 152x, Bromochloroacetic acid at 106x. Here's every one, what it does, and what takes it out.

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The numbers

Above EWG health guidelines

15

contaminants

Other contaminants detected

23

under the guideline

Tested for, not found

194

chemicals

People served

1,999,472

San Antonio Water System

Met federal legal limits in the latest quarter the EPA assessed (April 2024 - June 2024). Legal doesn't mean the water meets today's health guidelines: most legal limits haven't moved in about 20 years, and many of these chemicals have none. Bexar County, TX.

Contaminants Above EWG's Health Guidelines

Detected in 2021-2023 at annual averages over the level a public health authority considers safe. Most have no legal limit at all.

  • Haloacetic acids (HAA9)

    cancer

    161xEWG guideline

    This utility
    9.67 ppb
    EWG guideline
    0.06 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 23.9 ppb · US avg 23.7 ppb

    What is this contaminant?

    Haloacetic acids are formed when disinfectants such as chlorine are added to tap water. The group of nine haloacetic acids includes monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid, which are regulated as a group by the federal government (HAA5); and bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, and tribromoacetic acid.

    Where it comes from: treatment byproducts.

  • Total trihalomethanes (TTHMs)

    cancer

    152xEWG guideline

    This utility
    22.9 ppb
    EWG guideline
    0.15 ppb
    Legal limit
    80 ppb
    • Activated carbon
    • Reverse osmosis

    State avg 25.6 ppb · US avg 29.1 ppb

    What is this contaminant?

    Trihalomethanes are cancer-causing contaminants that form during water treatment with chlorine and other disinfectants. The total trihalomethanes group includes four chemicals: chloroform, bromodichloromethane, dibromochloromethane and bromoform.

    Where it comes from: treatment byproducts.

  • Bromochloroacetic acid

    106xEWG guideline

    This utility
    2.12 ppb
    EWG guideline
    0.02 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 3.82 ppb · US avg 2.8 ppb

    What is this contaminant?

    Bromochloroacetic acid is formed when chlorine or other disinfectants are used to treat drinking water. Bromochloroacetic acid and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy.

    Where it comes from: treatment byproducts.

  • Dibromoacetic acid

    80xEWG guideline

    This utility
    2.41 ppb
    EWG guideline
    0.03 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 2.64 ppb · US avg 1.13 ppb

    What is this contaminant?

    Dibromoacetic acid, one of the group of five haloacetic acids regulated by federal standards, is formed when chlorine or other disinfectants are used to treat drinking water. Haloacetic acids and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

    Where it comes from: treatment byproducts.

  • Bromodichloromethane

    cancer

    74xEWG guideline

    This utility
    4.42 ppb
    EWG guideline
    0.06 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 6.5 ppb · US avg 5.89 ppb

    What is this contaminant?

    Bromodichloromethane, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Bromodichloromethane and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

    Where it comes from: treatment byproducts.

  • Haloacetic acids (HAA5)

    cancer

    58xEWG guideline

    This utility
    5.76 ppb
    EWG guideline
    0.1 ppb
    Legal limit
    60 ppb
    • Activated carbon
    • Reverse osmosis

    State avg 12.5 ppb · US avg 19.8 ppb

    What is this contaminant?

    Haloacetic acids are formed when disinfectants such as chlorine are added to tap water. The group of five haloacetic acids regulated by federal standards includes monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid.

    Where it comes from: treatment byproducts.

  • Dibromochloromethane

    cancer

    55xEWG guideline

    This utility
    5.55 ppb
    EWG guideline
    0.1 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 5.95 ppb · US avg 3.55 ppb

    What is this contaminant?

    Dibromochloromethane, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Dibromochloromethane and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

    Where it comes from: treatment byproducts.

  • Nitrate and nitrite

    cancer

    14xEWG guideline

    This utility
    2.01 ppm
    EWG guideline
    0.14 ppm
    Legal limit
    10 ppm
    • Ion exchange
    • Reverse osmosis

    State avg 0.591 ppm · US avg 0.78 ppm

    What is this contaminant?

    Nitrate and nitrite enter water from fertilizer runoff, septic tanks and urban runoff. These contaminants can cause oxygen deprivation for infants and increase the risk of cancer. Nitrite is significantly more toxic than nitrate. Click here to read more about nitrate.

    Where it comes from: agriculture, runoff & sprawl, naturally occurring.

  • Dichloroacetic acid

    cancer

    10xEWG guideline

    This utility
    2.05 ppb
    EWG guideline
    0.2 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 6.77 ppb · US avg 8 ppb

    What is this contaminant?

    Dichloroacetic acid, one of the group of five haloacetic acids regulated by federal standards, is formed when chlorine or other disinfectants are used to treat drinking water. Haloacetic acids and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

    Where it comes from: treatment byproducts.

  • Nitrate

    cancer

    10xEWG guideline

    This utility
    1.42 ppm
    EWG guideline
    0.14 ppm
    Legal limit
    10 ppm
    • Ion exchange
    • Reverse osmosis

    State avg 0.525 ppm · US avg 0.824 ppm

    What is this contaminant?

    Nitrate, a fertilizer chemical, frequently contaminates drinking water due to agricultural and urban runoff, and discharges from municipal wastewater treatment plants and septic tanks. Excessive nitrate in water can cause oxygen deprivation in infants and increase the risk of cancer. Click here to read more about nitrate.

    Where it comes from: agriculture, runoff & sprawl, naturally occurring.

  • Chloroform

    cancer

    7xEWG guideline

    This utility
    2.82 ppb
    EWG guideline
    0.4 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 7.52 ppb · US avg 16.2 ppb

    What is this contaminant?

    Chloroform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Chloroform and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy.

    Where it comes from: treatment byproducts.

  • Chromium (hexavalent)

    cancer

    6.8xEWG guideline

    This utility
    0.136 ppb
    EWG guideline
    0.02 ppb
    Legal limit
    None
    • Ion exchange
    • Reverse osmosis

    State avg 0.32 ppb · US avg 0.44 ppb

    What is this contaminant?

    Chromium (hexavalent) is a carcinogen that commonly contaminates American drinking water. Chromium (hexavalent) in drinking water may be due to industrial pollution or natural occurrences in mineral deposits and groundwater. Read more about chromium (hexavalent).

    Where it comes from: industry, naturally occurring.

  • Radium, combined (-226 and -228)

    cancer

    6.8xEWG guideline

    This utility
    0.34 pCi/L
    EWG guideline
    0.05 pCi/L
    Legal limit
    5 pCi/L
    • Ion exchange
    • Reverse osmosis

    State avg 0.37 pCi/L · US avg 0.33 pCi/L

    What is this contaminant?

    Radium is a radioactive element that causes bone cancer and other cancers. It can occur naturally in groundwater, and oil and gas extraction activities such as hydraulic fracturing can elevate concentrations.

    Where it comes from: industry, naturally occurring.

  • Bromoform

    cancer

    5.9xEWG guideline

    This utility
    2.95 ppb
    EWG guideline
    0.5 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 3.34 ppb · US avg 1.44 ppb

    What is this contaminant?

    Bromoform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Bromoform and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

    Where it comes from: treatment byproducts.

  • Trichloroacetic acid

    cancer

    4.3xEWG guideline

    This utility
    0.428 ppb
    EWG guideline
    0.1 ppb
    Legal limit
    None
    • Activated carbon
    • Reverse osmosis

    State avg 2.14 ppb · US avg 6.57 ppb

    What is this contaminant?

    Trichloroacetic acid, one of the group of five haloacetic acids regulated by federal standards, is formed when chlorine or other disinfectants are used to treat drinking water. Haloacetic acids and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

    Where it comes from: treatment byproducts.

What Takes It Out

EWG lists which home filter technologies reduce each contaminant. Counted against this utility's report:

Reverse osmosis

15 of 15

contaminants above the guideline, plus 20 other detected. Reverse osmosis is the drinking water system under the sink.

Reverse Osmosis

Activated carbon

11 of 15

contaminants above the guideline, plus 9 other detected. Activated carbon is the whole-house filter on the main line.

Whole-House Filtration

Ion exchange

4 of 15

contaminants above the guideline. Ion exchange is what a water softener does; it also takes out the hardness that scales your fixtures.

Water Softeners

A complete system stacks all three: carbon on the main line, a softener, and reverse osmosis at the kitchen sink. One flat price, installed by a licensed plumber near you.

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Other Contaminants Detected

Found in the water, under EWG's guideline. Shown as a share of the guideline so you can see what's close.

ContaminantThis utilityOf the guidelineLegal limitWhat filters it
Thallium0.0500 ppb
50% of 0.1 ppb
2 ppbIon exchange, Reverse osmosis
Uranium0.14 pCi/L
33% of 0.43 pCi/L
20 pCi/LIon exchange, Reverse osmosis
Vanadium2.72 ppb
13% of 21 ppb
NoneIon exchange
Fluoride0.426 ppm
11% of the legal limit
4 ppmReverse osmosis
Barium62.0 ppb
9% of 700 ppb
2,000 ppbIon exchange, Reverse osmosis
Chlorate6.27 ppb
3% of 210 ppb
NoneActivated carbon, Reverse osmosis, Ion exchange
Molybdenum1.04 ppb
3% of 40 ppb
NoneIon exchange, Reverse osmosis
1,4-Dioxane0.00829 ppb
2% of 0.35 ppb
NoneReverse osmosis
Selenium0.1000 ppb
0% of 30 ppb
50 ppbReverse osmosis
Manganese0.299 ppb
0% of 100 ppb
NoneIon exchange
Chromium (total)0.243 ppb
0% of the legal limit
100 ppbIon exchange, Reverse osmosis
Monochloroacetic acid0.0921 ppb
0% of 53 ppb
NoneActivated carbon, Reverse osmosis
Monobromoacetic acid0.0277 ppb
0% of 25 ppb
NoneActivated carbon, Reverse osmosis
Strontium0.806 ppb
0% of 1,500 ppb
NoneIon exchange, Reverse osmosis
Perfluorobutanoic Acid (PFBA)0.536 ppt
0% of 1,000 ppt
NoneActivated carbon, Reverse osmosis
Cobalt0.00690 ppb
0% of 70 ppb
NoneIon exchange, Reverse osmosis
Perfluoropentanoic Acid (PFPeA)0.0760 ppt
0% of 1,000 ppt
NoneActivated carbon, Reverse osmosis
Perfluorobutane sulfonate (PFBS)0.0880 ppt
0% of 2,000 ppt
NoneActivated carbon, Reverse osmosis
Xylenes (total)0.0123 ppb
0% of 1,800 ppb
10,000 ppbActivated carbon, Reverse osmosis
2-methyl-1-propene5.00 ppb
No guideline
NoneActivated carbon, Reverse osmosis
Hexadecanoic acid3.91 ppb
No guideline
NoneActivated carbon, Reverse osmosis
Lithium9.45 ppb
No guideline
NoneIon exchange, Reverse osmosis
Octadecanoic acid6.15 ppb
No guideline
NoneActivated carbon, Reverse osmosis
194 chemicals tested for and not foundShow the list

1,1,1,2-Tetrachloroethane, 1,1,1-Trichloroethane, 1,1,2,2-Tetrachloroethane, 1,1,2-Trichloroethane, 1,1-Dichloroethane, 1,1-Dichloroethylene, 1,1-Dichloropropene, 1,2,3-Trichlorobenzene, 1,2,3-Trichloropropane, 1,2,4-Trichlorobenzene, 1,2,4-Trimethylbenzene, 1,2-Dibromo-3-chloropropane (DBCP), 1,2-Dichloroethane, 1,2-Dichloropropane, 1,3,5-Trimethylbenzene, 1,3-Butadiene, 1,3-Dichloropropane, 1-butanol, 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic aci, 17-beta-Estradiol, 2,2-Dichloropropane, 2,3-Dichlorobiphenyl, 2,4,5-T, 2,4,5-TP (Silvex), 2,4,5-Trichlorobiphenyl, 2,4-DB, 2-Chlorobiphenyl, 2-Hexanone, 2-methoxyethanol, 2-propen-1-ol, 22'3'46-Pentachlorobiphenyl, 22'33'44'6-Heptachlorobiphenyl, 22'33'45'66'-Octachlorobiphenyl, 22'44'-Tetrachlorobiphenyl, 22'44'56'-Hexachlorobiphenyl, 3,5-Dichlorobenzoic acid, 3-Hydroxycarbofuran, 4,8-dioxa-3H-perfluorononanoic acid (ADONA), 4-Androstene-3,17-dione, 4:2 Fluorotelomer Sulfonic Acid (4:2 FTSA), 6:2 Fluorotelomer Sulfonic Acid (6:2 FTSA), 8:2 Fluorotelomer Sulfonic Acid (8:2 FTSA), 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (, Acenaphthene, Acenaphthylene, Acifluorfen (Blazer), Acrylonitrile, Alachlor (Lasso), Aldicarb, Aldicarb sulfone, Aldicarb sulfoxide, Aldrin, alpha-Chlordane, Alpha-hexachlorocyclohexane, Aluminum, Anthracene, Antimony, Arsenic, Asbestos, Atrazine, Baygon (Propoxur), Bentazon (Basagran), Benzene, Benzo[a]anthracene, Benzo[a]pyrene, Benzo[b]fluoranthene, Benzo[g,h,i]perylene, Benzo[k]fluoranthene, Beryllium, Bromacil, Bromobenzene, Bromochloromethane, Bromomethane, Butachlor, Butanoic acid, 2,2,3,3,4,4-hexafluoro-4-(trifluoro, Butyl benzyl phthalate, Butylated hydroxyanisole, Cadmium, Carbaryl, Carbofuran, Carbon tetrachloride, Chloramben, Chlordane, Chlorodifluoromethane, Chloroethane, Chloromethane, Chlorpyriphos, Chrysene, cis-1,2-Dichloroethylene, cis-1,3-Dichloropropene, Cyanide, Dalapon, Di(2-ethylhexyl) adipate, Di-n-butyl phthalate, Dibenz[a,h]anthracene, Dibromomethane, Dicamba, Dichlorodifluoromethane, Dichloromethane (methylene chloride), Dichlorprop, Dieldrin, Diethyl phthalate, Dimethipin, Dimethyl phthalate, Dinoseb, Endrin, Equilin, Estriol, Estrone, Ethinyl estradiol, Ethoprop, Ethyl methacrylate, Ethylene dibromide, Fluorene, gamma-Chlordane, Germanium, Heptachlor, Heptachlor epoxide, Hexachlorobenzene (HCB), Hexachlorobutadiene, Hexachlorocyclopentadiene, Hexafluoropropylene oxide dimer acid (HFPO-DA), Indeno[1,2,3-cd]pyrene, Iodomethane, Isopropylbenzene, Lindane, m-Dichlorobenzene, Mercury (inorganic), Methiocarb, Methomyl, Methoxychlor, Methyl isobutyl ketone, Methyl methacrylate, Metolachlor, Metribuzin, Monochlorobenzene (chlorobenzene), MTBE, n-Butylbenzene, N-ethyl perfluorooctane sulfonamido acetic acid (N, N-methyl perfluorooctanesulfonamidoacetic acid, n-Propylbenzene, Naphthalene, Nitrite, Nonafluoro-3,6-dioxaheptanoic acid, o-Chlorotoluene, o-Dichlorobenzene, o-toluidine, Oxamyl (Vydate), Oxyflurofen, p-Chlorotoluene, p-Dichlorobenzene, p-Isopropyltoluene, Pentachlorophenol, Perfluoro(2-ethoxyethane)sulfonic acid, Perfluorodecanoic acid (PFDA), Perfluorododecanoic acid (PFDoA), Perfluoroheptane sulfonic acid (PFHpS), Perfluoroheptanoic acid (PFHPA), Perfluorohexane sulfonate (PFHXS), Perfluorohexanoic Acid (PFHxA), Perfluorononanoic acid (PFNA), Perfluorooctane sulfonate (PFOS), Perfluorooctanoic acid (PFOA), Perfluoropentane sulfonic acid (PFPeS), Perfluorotetradecanoic acid (PFTA), Perfluorotridecanoic acid (PFTrDA), Perfluoroundecanoic acid (PFUnA), Permethrin, Phenanthrene, Picloram, Polychlorinated biphenyls (PCBs), Profenofos, Propachlor, Propanoic acid, 2,2,3,3-tetrafluoro-3-(trifluorome, Pyrene, Quinclorac, Quinoline, sec-Butylbenzene, Silver, Simazine, Styrene, Tebuconazole, tert-Butylbenzene, Testosterone, Toluene, Toxaphene, trans-1,2-Dichloroethylene, trans-1,3-Dichloropropene, trans-Nonachlor, Tribufos, Trichloroethylene, Trichlorofluoromethane, Trifluralin, Vinyl chloride.

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We install in San Antonio. Water softener installation in San Antonio, TX

Source: the EWG Tap Water Database, built from San Antonio Water System's own testing in 2021-2023, as reported to the state and the EPA. Legal limits are federal (or state) maximums; health guidelines are the levels EWG's scientists consider protective, usually set by a state or federal public health authority. “Times over” compares the utility's annual average with the guideline. Last pulled October 2026.Hardness isn't in EWG's data; ours is an area estimate.

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Your utility's own test results, from the EWG Tap Water Database: what's in the water, how it compares with health guidelines, and what takes it out.

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