Updated November 1, 2026

Houston tap water, read line by line from the 2025 report

Houston Water serves 2.97 million customers across more than 650 square miles and pumps about 500 million gallons a day. Its annual report is dense, so here is what the numbers say for the main city system (TX1010013) and what is worth acting on.

Lakes north and east, wells underneath

In 2025, 90.3% of the main system's water was surface water and 9.7% was groundwater. The surface water comes from two river basins: the San Jacinto, through Lake Conroe and Lake Houston, and the Trinity, through Lake Livingston. The groundwater comes from 104 wells drilled more than 750 feet into the Evangeline and Chicot aquifers.

The report also covers five smaller systems the city runs: Kingwood, Willow Chase, District 73, District 82 and Belleau Woods. Each has its own ID and its own table. If you live in one of those areas, look up your own system's numbers rather than the main-system figures below.

The two 2025 violations, in plain terms

Houston's report lists two violations for 2025, and neither was a contaminant over a health limit.

• May 2025: turbidity. A single combined-filter effluent reading went over the turbidity limit. The report's plant table shows 95% of samples at or under 0.3 NTU in the lowest month and a single highest reading of 1.95 NTU. Turbidity, or cloudiness, has no health effect of its own. It is regulated because it can shield microbes from disinfection. EPA's compliance record lists the violation as resolved.
• September 2025: chlorite monitoring. The city failed to monitor and report chlorite, a disinfection byproduct, as required for the month. That is a paperwork and sampling lapse, not a measured exceedance. Chlorite results reported elsewhere in the table peaked at 0.1 ppm, against a limit of 1 ppm.

Hardness swings with the source

Total hardness at the main system's plants ran from 43.5 to 229 ppm in 2025, averaging 135.5 ppm. That's about 7.9 grains per gallon on average, which counts as hard on the usual scale, though the low end is close to soft. Total dissolved solids averaged 260 ppm. If you're weighing a softener, test your own tap first, because the system average hides a wide range. Then size it with our softener sizing calculator.

Chloramine, not chlorine

Houston disinfects with chloramines. Distribution samples averaged 2.8 ppm, with individual readings from 0.04 to 4.8 ppm. The 4.0 ppm limit applies to a running average, not to single samples. Chloramine lasts longer in pipes than chlorine and forms fewer byproducts. The highest locational running average for haloacetic acids was 40.8 ppb, under the 60 ppb limit. It also behaves differently at home: it takes longer to dissipate from a glass left on the counter, and fish tanks need a dechloraminating conditioner.

What federal PFAS sampling found

Under EPA's UCMR 5 program, the city system was sampled 96 times for each compound. Four PFAS turned up at low levels. The most frequent was PFHxA (16 detections, maximum 5.1 ppt). The highest single value was 6:2 FTS at 42.6 ppt, found in 10 of 96 samples. PFBA and PFPeA were found at single-digit ppt. PFOA and PFOS, the two compounds with the strictest new federal limits, were not among the detections. Lithium, also tracked under UCMR 5, averaged 23.8 ppb in 2024.

Your service line

The 90th-percentile lead result in EPA's compliance data is 5 ppb, against the 15 ppb action level. The city has posted a service line inventory map at bit.ly/HouLCRRMap. If your line is listed as unknown, the city asks you to self-report its material with photos. For a lead or PFAS filter, our filter selector matches certifications to concerns.