San Antonio’s hard water is not a rumor. SAWS, the San Antonio Water System, says the typical hardness of the water it provides ranges from 15 to 20 grains per gallon. This guide explains where that hardness comes from, how the figure compares with the scale the US Geological Survey uses, and what it means in your kitchen and bathroom.
Water Filtration San Antonio is an independent referral service, not an installer or plumber. When you send the form, your details go to an independent local water treatment pro who can contact you and quote the work.
Where the hardness comes from
Hardness is caused by compounds of calcium and magnesium, and by a variety of other metals, dissolved in water (USGS). SAWS says the hardness in its water comes from calcium carbonate that occurs naturally in water from the Edwards and the Trinity Aquifers.
Grains per gallon and mg/L
Hardness is given in two units. Utilities and softener makers use grains per gallon (gpg). Scientists and the USGS use milligrams per liter (mg/L) as calcium carbonate. One grain per gallon is about 17 mg/L.
| USGS grade | mg/L as calcium carbonate | About, in grains per gallon |
|---|---|---|
| Soft | 0 to 60 | 0 to 3.5 |
| Moderately hard | 61 to 120 | 3.6 to 7 |
| Hard | 121 to 180 | 7.1 to 10.6 |
| Very hard | Over 180 | Over 10.6 |
| SAWS typical range | Roughly 255 to 340 | 15 to 20 |
The grain column is worked out at 17 mg/L per grain, so treat it as approximate. Either way, SAWS’s range is well inside the very hard band.
What hard water does, and does not do
SAWS says it plainly: “Hard water is not a health hazard.” Water utilities commonly add that hard water does not pose a health risk and that there is no health-based drinking water standard for it. The EPA’s list of secondary standards for taste, color and odor has no number for hardness either.
What hard water does is practical. In hard water, soap reacts with the calcium to form soap scum, and more soap or detergent is needed to get things clean (USGS). Deposits build up on dishes, fixtures and basins, and scale can build up on pipes.
- Crust around faucets, shower heads and drains
- Spots on glasses and dishes
- Soap scum in the tub and shower
- Scale inside kettles, coffee makers and pipes
Tired of scale? Ask an independent San Antonio pro about a softener.
Request a quoteIf you are not a SAWS customer
The 15 to 20 grain figure is for water SAWS provides. Some homes around San Antonio are supplied by another utility, and their water may be harder or softer. Your water bill names your supplier. Ask that utility for its annual water quality report and use its hardness figure, not SAWS’s. If you are on a private well, a lab test of your own water is the only figure that applies.
Checking your own tap
SAWS’s range is a typical figure for its supply. Your own tap is worth testing, for two reasons: the SAWS figure is typical, not a reading for your house, and if you already have a softener, a test before and after it shows whether it is working. Hardness test strips or a test by a water treatment pro give a reading in grains per gallon. Write it down with the date.
If the reading after your softener is close to the reading before it, the softener is not doing its job: see softener repair.
What you can do about it
Hardness is removed with a water softener; NSF/ANSI 44 is the standard for residential softeners. A carbon filter does not remove it. The water softener page explains sizing for SAWS water, and installation covers the city permit and the Texas license. If you are not ready for a softener, a hardness test at your tap tells you exactly what you are dealing with.
Questions people ask
How hard is San Antonio water?
SAWS gives a typical hardness of 15 to 20 grains per gallon for the water it provides, roughly 255 to 340 mg/L. The USGS calls over 180 mg/L very hard.
Why is San Antonio water so hard?
SAWS says the hardness comes from calcium carbonate found naturally in water from the Edwards and the Trinity Aquifers.
Is San Antonio hard water bad for you?
SAWS says hard water is not a health hazard. Its effects are scale, spots and soap scum.
Does a water filter remove hardness?
No. A carbon filter is for taste, odor or specific contaminants. Hardness is removed by a softener certified to NSF/ANSI 44.
My suburb is not on SAWS. How hard is my water?
Ask the utility named on your water bill for its annual water quality report, or test your tap. SAWS’s figure applies only to water SAWS provides.
