Short answer: In the 2022–2024 records we hold for San Marcos, no listed result is above a legal limit, but a health-based violation is on record (EPA SDWIS). Also worth knowing: lithium sits above a screening level. 5 substances were detected and 26 were tested and not detected. The water is from City of San Marcos, serving 72,970 residents.
Your water bill or annual water quality report names your actual supplier.
Surface water
The treatment details are not on record.
Mains, then your building’s service line.
Plumbing inside the building is outside this record.
No measured result is above a legal limit; lithium sits above a screening level.
11.3 µg/L, sampled 2023-11-14 to 2024-08-15. EPA UCMR 5.
10 µg/L EPA health reference level (screening, not a legal limit).
Detected at up to 11.3 µg/L (above the 10 µg/L EPA health reference level; a screening level, not a legal limit).
Where it enters is not in this record.
Test your own tap first. To reduce it: Depends on the contaminant (The certifier's listing for each named contaminant).
3.4 ng/L, sampled 2023-11-14 to 2024-08-15. EPA UCMR 5.
10 ng/L federal MCL (2024): a legal limit. That limit is judged on a yearly average, and water systems have until 2029 to meet it.
Detected at up to 3.4 ng/L (below the 10 ng/L limit EPA set in 2024). That limit is judged on a yearly average, and water systems have until 2029 to meet it.
Comes with the source water; home plumbing does not add it.
Test your own tap first. To reduce it: Reverse osmosis, or carbon certified for PFAS (NSF/ANSI 53 or 58, with PFHxS named on the listing).
1.63 µg/L, sampled 2022–2024 monitoring period. EPA SDWIS (Lead & Copper Rule).
15 µg/L federal action level. EPA health goal (MCLG): 0.
The 90th-percentile tap result was 1.63 µg/L (below the 15 µg/L action level).
Usually from lead service lines, solder and fixtures inside buildings, after the water leaves treatment.
Test your own tap first. To reduce it: Lead-certified carbon filter, or reverse osmosis (NSF/ANSI 53 (lead)).
11.4 ng/L, sampled 2023-11-14 to 2024-08-15. EPA UCMR 5.
No federal limit is on record for it.
Detected at up to 11.4 ng/L. No federal or state limit exists for this substance; shown for transparency, not graded.
Comes with the source water; home plumbing does not add it.
Test your own tap first. To reduce it: Reverse osmosis, or carbon certified for PFAS (NSF/ANSI 53 or 58, with PFBA named on the listing).
4.2 ng/L, sampled 2023-11-14 to 2024-08-15. EPA UCMR 5.
No federal limit is on record for it.
Detected at up to 4.2 ng/L. No federal or state limit exists for this substance; shown for transparency, not graded.
Comes with the source water; home plumbing does not add it.
Test your own tap first. To reduce it: Reverse osmosis, or carbon certified for PFAS (NSF/ANSI 53 or 58, with PFPeA named on the listing).
CITY OF SAN MARCOS (EPA PWSID TX1050001) delivers surface water to 72,970 residents. This report reflects 29 individual PFAS result(s) from the source UCMR5 observations and the latest Lead & Copper Rule 90th-percentile result. Water hardness and disinfectant type are pending the utility's own annual report.
1health-based violation in the last 10 years
From EPA SDWIS. Counted once per contaminant per year, as in the Track record score.
No result is not a pass. Your utility's annual water quality report may list them, and a certified lab test covers your own tap.
Every filing is listed; the Track record score counts at most one per contaminant per year.
Resolved
to Resolved
The record describes water leaving treatment and samples across the system. Pipes, solder and fixtures inside a building can add lead the record can’t see, especially in older buildings with lead service lines.
Test your waterMeasured in this report
Sampled across the system
Not in this record
Only a tap test measures it
Know what comes from your tap, starting with a first-draw lead sample.
Compare each result with its named reference in our test reader.
Choose a technology certified for what your test found.
Screening tells you if something is worth a closer look; a lab result is the number you can act on.
As an Amazon Associate, PurityMap earns from qualifying purchases. Affiliate disclosure.
Lab-certified results
ETR Laboratories
50+ substances, including lead, copper, arsenic, nitrate, hardness and coliform bacteria
What it can't tell you: It does not test PFAS, and not every result on the panel falls under the lab's accredited scope.
Screening: quick check, not lab-grade
Safe Home (EnviroTestKits)
Lead, read as one of three ranges: 0–4, 5–15 or 15+ ppb
What it can't tell you: It shows a lead range, not an exact level, and tests nothing else unless you pay extra for the optional lab test.
When your results arrive, read them here → · Compare every kit we list
Texas Commission on Environmental Quality certifies the labs that test drinking water in Texas. Find a certified lab in Texas ↗ · What lab tests cost →
| Finding | Reference type | Technology | Certification to check |
|---|---|---|---|
| Lithium11.3 µg/L | Screening level | Depends on the contaminant | The certifier's listing for each named contaminant |
| Perfluorohexanesulfonic acid (PFHxS)3.4 ng/L | Federal MCL | Reverse osmosis, or carbon certified for PFAS | NSF/ANSI 53 or 58, with PFHxS named on the listing |
| Lead (90th percentile)1.63 µg/L | Action level | Lead-certified carbon filter, or reverse osmosis | NSF/ANSI 53 (lead) |
| Perfluorobutanoic acid (PFBA)11.4 ng/L | No federal limit | Reverse osmosis, or carbon certified for PFAS | NSF/ANSI 53 or 58, with PFBA named on the listing |
| Perfluoropentanoic acid (PFPeA)4.2 ng/L | No federal limit | Reverse osmosis, or carbon certified for PFAS | NSF/ANSI 53 or 58, with PFPeA named on the listing |
Each card names which San Marcos findings its current certification covers, and which it doesn't.
As an Amazon Associate, PurityMap earns from qualifying purchases. A product appears here only when a current certification record covers at least one identified concern; every concern stays listed. The retail offer is looked up afterwards and never changes which products appear or their order. Affiliate disclosure.
Lead service lines
City of San Marcos reported 1,515 galvanized service lines to replace in EPA’s inventory (2026Q2). Many utilities replace these lines for free or share the cost. Ask City of San Marcos whether your home’s line is on its list before you pay anyone.
Local help
Call to be connected with a local plumbing provider about lead service lines, repiping or fixture replacement.
Older buildings may have lead service lines, solder or fixtures. San Marcos’ record shows lead at 1.63 µg/L (15 µg/L federal action level). Test first-draw water, then filter if needed.
3 of 29 PFAS tested were detected in San Marcos’ record (PFHxS 3.4 ng/L, PFBA 11.4 ng/L and PFPeA 4.2 ng/L). If PFAS matters to you, a filter certification names each compound it covers.
Most utilities keep chlorine or chloramine in the pipes. A carbon filter certified for taste and odor reduces either; your utility can tell you which it uses.
Your utility’s annual water quality report usually lists hardness; a test strip also measures it.
Reverse osmosis reduces many dissolved contaminants, including lead and minerals, at a single faucet, with some water sent to drain.
Get one email when San Marcos’ record changes.
One email when a new sampling round is published, a result moves above or below its reference, or the system's score changes.PurityMap does not give a safe/unsafe verdict; it shows what the public records measured. For San Marcos, PFAS were detected below their limits, and PFBA 11.4 ng/L and PFPeA 4.2 ng/L with no federal or state limit; the lead 90th-percentile result was 1.63 µg/L against the 15 µg/L action level. CITY OF SAN MARCOS (PWSID TX1050001) has a Purity Score of 89/100 (confidence: moderate), assessed at the water-system level and computed only from contaminants that were measured. Water can change in your own pipes, so a certified test is the only way to know what comes out of your tap. What we found →
CITY OF SAN MARCOS (PWS ID TX1050001) is the public water system on record for San Marcos, Texas, serving about 72,970 people. Confirm the utility on your water bill before acting on a specific finding. Water utility →
Surface water (primary source of record in EPA SDWIS). Water utility →
In EPA's UCMR 5 testing (2023-11-14 to 2024-08-15), PFHxS was detected at 3.4 ng/L, below the 10 ng/L federal limit. PFBA (11.4 ng/L) and PFPeA (4.2 ng/L) were also detected; they have no federal or state limit. What we found →
CITY OF SAN MARCOS's most recent lead 90th-percentile result (2022–2024) was 1.63 µg/L, below the 15 µg/L action level. That figure comes from sampled homes; lead usually enters from a building's own pipes and fixtures, so only a test at your tap tells you what you drink. Your household →
PurityMap's current record for San Marcos holds 31 findings: 1 above a reference, 2 detected within the reference, 2 detected with no limit and 26 not detected. Each finding links to its dated public record; a parameter that was never monitored is shown as pending, not as a pass. Records →
| Contaminant | Measured | Reference | Sampled | Source |
|---|---|---|---|---|
| Lithium | 11.3 µg/L | 10 µg/L EPA health reference level (screening, not a legal limit) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorohexanesulfonic acid (PFHxS) | 3.4 ng/L | 10 ng/L federal MCL (2024) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Lead (90th percentile) | 1.63 µg/L | 15 µg/L federal action level | 2022–2024 | EPA SDWIS (Lead & Copper Rule) ↗ (opens in a new tab) |
| Perfluorobutanoic acid (PFBA) | 11.4 ng/L | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoropentanoic acid (PFPeA) | 4.2 ng/L | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS) | < 5 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS) | < 5 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS) | < 5 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| 4,8-Dioxa-3H-perfluorononanoic acid (ADONA) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS) | < 2 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals) | < 5 ng/L (not detected) | 10 ng/L federal MCL (2024) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA) | < 5 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA) | < 6 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Nonafluoro-3,6-dioxaheptanoic acid (NFDHA) | < 20 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoro-3-methoxypropanoic acid (PFMPA) | < 4 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoro-4-methoxybutanoic acid (PFMBA) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorobutanesulfonic acid (PFBS) | < 3 ng/L (not detected) | 2,000 ng/L EPA health advisory (screening, not a legal limit) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorodecanoic acid (PFDA) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorododecanoic acid (PFDoA) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoroheptanesulfonic acid (PFHpS) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoroheptanoic acid (PFHpA) | < 3 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorohexanoic acid (PFHxA) | < 3 ng/L (not detected) | 400,000 ng/L Michigan EGLE state MCL (strictest US state) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorononanoic acid (PFNA) | < 4 ng/L (not detected) | 10 ng/L federal MCL (2024) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorooctanesulfonic acid (PFOS) | < 4 ng/L (not detected) | 4.0 ng/L federal MCL (2024) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorooctanoic acid (PFOA) | < 4 ng/L (not detected) | 4.0 ng/L federal MCL (2024) | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoropentanesulfonic acid (PFPeS) | < 4 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorotetradecanoic acid (PFTA) | < 8 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluorotridecanoic acid (PFTrDA) | < 7 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
| Perfluoroundecanoic acid (PFUnA) | < 2 ng/L (not detected) | No federal or state limit; shown for transparency | 2023–2024 | EPA UCMR 5 ↗ (opens in a new tab) |
UCMR5 Analytical Results
UCMR5 Analytical Results: CITY OF SAN MARCOS (TX1050001)
US EPA
State SDWIS Compliance Record
Lead & Copper Rule 90th-percentile: CITY OF SAN MARCOS (TX1050001)
US EPA SDWIS
Methodology: how we analyze water. Prepared with AI assistance and reviewed by the PurityMap Editorial Team before publication.
EPA SDWIS, EPA UCMR 5 and utility reports, each dated and linked.
Units converted to one basis; a non-detect kept distinct from zero.
Each result tagged by reference type: MCL, action level, screening level or aesthetic.
Every value sits against its own reference, never a blended one.
Measured subjects summarised at the water-system level; an open health-based violation caps the score.
Treatment is matched to what was found; a product is called certified only when its current certification names it.
What the Purity Score means: a summary of this water system’s published record, capped while a health-based violation is open. It is not a test of any tap. CITY OF SAN MARCOS · PWSID TX1050001 · Purity Score 89/100 (Good) · Confidence: moderate · Assessed at the water-system level
Full methodology →Start with the hot-or-cold tap check. Where City of San Marcos reported something related, it's shown below.
Lead at City of San Marcos: 1.63 µg/L (90th percentile, 2022–2024 monitoring period). Lead has no taste, so a taste neither shows nor rules it out.