Austin vs.
San Antonio vs.
Houston vs.
Dallas.

Understanding the Texas water quality story starts with geology and ends with treatment infrastructure. These four cities are drawing from fundamentally different hydrological systems — which explains why their water challenges are so distinct, even though all four face the same universal Texas problem: disinfection by-products from chloramine treatment.

Austin's water tells a limestone surface water story. The Colorado River originates in the Texas Hill Country and drains across Edwards Limestone terrain before filling Lake Travis and Lake Austin. By the time that water reaches an Austin tap, it has absorbed significant calcium and magnesium — hence 14–16 GPG hardness. Austin Water uses chloramines for disinfection, a method that effectively controls bacteria but produces TTHMs and HAA5 disinfection by-products, and is effectively invisible to standard carbon filters. The good news is that Austin's source water — Highland Lakes reservoirs — is relatively protected from industrial contamination compared to the river systems feeding Houston and Dallas.

San Antonio's Edwards Aquifer is simultaneously a gift and a curse. The Edwards Aquifer produces some of the purest-tasting water naturally — it's spring-fed, filtered through centuries of limestone, and has historically tested clean for many industrial contaminants. The problem is that exact same limestone filtration loads the water with calcium and magnesium to an extreme degree. At 15–18 GPG, San Antonio homeowners face the steepest scale damage costs in Texas. SAWS also reports the highest number of EWG contaminant exceedances of the four cities — partly driven by naturally occurring radium in aquifer water and elevated DBPs from the treatment process. Moving from Houston to San Antonio without installing a water softener is an appliance-destroying mistake many new residents make only once.

Houston's challenge is almost the inverse of San Antonio's. Gulf Coastal Plain surface water is naturally soft — under 6 GPG, a level that barely registers as "hard" by national standards. Houston residents who move from Central Texas and take a shower for the first time are often startled by how different the water feels. Soap lathers easily. No scale on showerheads. But Houston's aging distribution network — nearly half the water mains pre-date 1980 — creates leaching and microbial risk at the tap level that the treatment plant cannot fully anticipate. Houston homeowners should be less worried about hardness and more focused on point-of-use filtration that addresses PFAS, DBPs, and any intrusion from aging pipes.

Dallas occupies an interesting middle position. Drawing from multiple Trinity River reservoirs (Lake Lewisville, Lake Ray Hubbard, Lake Grapevine), Dallas has harder water than Houston but softer than Austin. Its treatment programme — which includes a pre-ozonation step — produces the best community taste scores of the four cities, likely by neutralising the geosmin and MIB compounds that give surface water a musty character in summer. Dallas also has the newest distribution infrastructure of the four cities, which lowers the leaching risk profile. For relocating families, Dallas represents a reasonable balance: not the hardest, not the most contaminated, and the best-tasting of the group.

What does this mean for someone moving between these cities? If you're relocating from Houston to Austin, prepare for a dramatic hardness increase — your water heater and dishwasher will notice immediately. If you're moving from Austin to San Antonio, add a water softener to your moving checklist, not your six-month wishlist. If you're arriving from outside Texas entirely, understand that all four cities use chloramines — standard pitcher filters and ordinary carbon blocks will not adequately address your new tap water regardless of which Texas city you land in. And in every city: PFAS are present, and reverse osmosis is the only NSF-certified technology that reliably removes them.