Houston water hardness: what the city report says

Close-up of a chrome shower head with water droplets

Houston tap water is hard on average: about 7.9 grains per gallon (135.5 ppm). That figure is for the Main System in the City of Houston's 2025 water quality report (PDF, opens in new tab). Samples ranged from 43.5 to 229 ppm, or about 2.5 to 13.4 grains per gallon.

Houston water hardness

Grains per gallon, from the City of Houston 2025 water quality report. Sacramento river water shown for comparison.

Houston Main System, 20252.5 to 13.4 gpg, avg 7.9

Sacramento, Sacramento River plant (comparison)2.0 gpg

03.5 soft7 hard10.5 very hard30 gpg

SoftModerately hardHardVery hard

Where does Houston water come from?

The city's report says Houston makes its drinking water from both surface water and groundwater. The surface water comes from the Trinity River and Lake Livingston, and from the San Jacinto River, Lake Conroe and Lake Houston. The groundwater comes from the Chicot and Evangeline aquifers.

Lake water and well water pick up different amounts of calcium and magnesium. That is why one part of Houston can be close to soft while another is very hard. The city runs six water systems in total, and the numbers here are for the Main System, which serves most homes.

What this means at home

White scale on faucets and shower heads
Spots on dishes, especially in harder areas
Scale inside water heaters over time
Soap scum on tubs and shower doors

Do you need a water softener in Houston?

It depends on your address. At the citywide average of about 8 grains per gallon, many homes will notice scale and spots, and a softener helps. If your area gets mostly lake water, you may be well under that and can skip it. A tap test tells you which group you are in.

Not sure? Read do I need a water softener with city water? or see what a softener costs.

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Common questions

Is Houston water hard?

On average, yes. The City of Houston's 2025 report lists total hardness for the Main System at 43.5 to 229 ppm, with an average of 135.5 ppm. That is about 7.9 grains per gallon, which counts as hard.

Why does Houston water hardness vary so much?

Houston uses both surface water from lakes and rivers and groundwater from the Chicot and Evangeline aquifers. These sources carry different amounts of minerals, so hardness changes by area and over time.

What softener setting should I use in Houston?

Test your own tap first. The citywide average is about 8 grains per gallon, but the range runs from about 2.5 to 13.4, so one setting does not fit everyone.