Texas Water Hardness by City: A Reference Guide for Facility Managers
Most major Texas cities have hard to very hard water, typically 10–25+ grains per gallon (gpg). San Antonio's Edwards Aquifer supply is among the hardest in the state at 15–20+ gpg. Houston, Austin, Dallas, and Fort Worth all fall in the 8–15 gpg range, though hardness varies by neighborhood and water source. Commercial and industrial facilities in any of these metros should plan on water softening as a baseline requirement to protect plumbing, boilers, cooling towers, and process equipment.
How Water Hardness Is Measured
Water hardness is the concentration of dissolved calcium and magnesium ions, expressed in two common units:
- Grains per gallon (gpg) — the unit used for sizing softeners in the US.
- Parts per million (ppm) or milligrams per liter (mg/L) — used in municipal water-quality reports.
To convert ppm to gpg, divide by 17.1. A municipal report listing 200 ppm hardness equals roughly 11.7 gpg.
The US Geological Survey classifies hardness as follows:
| Classification | gpg | ppm (mg/L as CaCO₃) |
|---|---|---|
| Soft | 0–1 | 0–17 |
| Slightly hard | 1–3.5 | 17–60 |
| Moderately hard | 3.5–7 | 60–120 |
| Hard | 7–10.5 | 120–180 |
| Very hard | 10.5+ | 180+ |
Most of Texas falls firmly in the "very hard" category.
Hardness by Metro Area
The numbers below are typical ranges drawn from the most recent published Consumer Confidence Reports (CCRs) for each city's municipal water utility. Facility-specific values can differ — always confirm with a current lab test before sizing equipment.
Houston
- Typical range: 8–13 gpg (about 140–220 ppm)
- Source water: Blend of surface water from Lake Houston, Lake Conroe, and Trinity River, supplemented by groundwater
- Notes: Hardness varies by service area within the Houston metro. Surface-water-dominated zones tend toward the lower end of the range; groundwater-supplied areas (some northern and western suburbs) can run higher.
San Antonio
- Typical range: 15–20+ gpg (about 250–350+ ppm)
- Source water: Primarily the Edwards Aquifer, a limestone karst formation
- Notes: Among the hardest municipal water in Texas. Because the aquifer flows through limestone, calcium carbonate dissolves into the supply continuously. Scaling control is not optional for any commercial steam, hot water, or cooling system in this area.
Austin
- Typical range: 10–15 gpg (about 170–260 ppm)
- Source water: Highland Lakes system on the Colorado River (Lake Travis, Lake Austin)
- Notes: Surface water, but the watershed runs through limestone country, so hardness stays in the "hard to very hard" range.
Dallas
- Typical range: 8–12 gpg (about 140–200 ppm)
- Source water: Lake Ray Hubbard, Lake Tawakoni, Lake Lewisville, and other reservoirs
- Notes: Generally on the softer end of Texas hardness, but still well above the threshold where scale forms in heat-transfer equipment.
Fort Worth
- Typical range: 9–13 gpg (about 150–220 ppm)
- Source water: Eagle Mountain Lake, Lake Worth, Lake Bridgeport, and Cedar Creek Reservoir
- Notes: Similar profile to Dallas. Some industrial sites in the DFW region use well water, which can run significantly harder.
What Hardness Means for Commercial Facilities
Above about 7 gpg, hardness begins to cause measurable problems:
- Scale on heat-transfer surfaces. Every 1/16-inch of scale on a boiler tube can increase fuel consumption by 5–10%.
- Reduced equipment life on dishwashers, ice machines, cooling towers, steam generators, and laundry equipment.
- Higher chemical costs for soaps, detergents, and CIP (clean-in-place) chemistry.
- Spotting and filming on glassware, dishes, and finished products.
- Membrane fouling on reverse osmosis systems if hardness isn't removed upstream.
For most commercial and industrial sites in Texas, the question isn't whether to soften — it's how to size the system correctly.
Sizing a Softener for Texas Water
The grain load on a softener equals hardness (gpg) × daily water use (gallons). A 200-room hotel using 30,000 gallons per day with 15 gpg hardness has a grain load of 450,000 grains per day. Sized to regenerate every 5 days, that hotel needs roughly 2.25 million grains of capacity — typically a twin-alternating system with high-capacity resin tanks.
For full sizing methodology, see our commercial water softener page or use the water hardness calculator in our Resources section.
When to Call Us
If you operate a commercial, industrial, healthcare, hospitality, or food and beverage facility anywhere in Texas, hardness is a system design parameter you can't ignore. Mueller Water Conditioning has been sizing, installing, and servicing softeners for Texas businesses since 1969, with offices in Houston, San Antonio, Austin, and DFW.
Call 1-888-678-6411 or request a quote.