Southlake water hardness ranges from 100 to 171 ppm in the city’s 2023 report, and from 108 to 150 ppm in Fort Worth’s 2025 report. Southlake buys all of its water from Fort Worth. This post reads both reports for pool owners. Figures are as of October 2026.
Where does Southlake’s water come from?
Southlake’s 2023 report says the city gets all its water from the City of Fort Worth. Fort Worth draws from surface water: Lake Worth, Eagle Mountain Lake, Lake Bridgeport, Richland Chambers Reservoir, Cedar Creek Reservoir and the Clear Fork Trinity River.
Fort Worth’s 2025 report says it adds monochloramines (chlorine and ammonia) to protect the water as it travels through the pipes. That is a drinking water treatment. It is not a pool chlorine reading.
What do the reports say about hardness, pH and alkalinity?
The two reports list a similar set of numbers. Southlake’s 2023 report holds 2022 data. Fort Worth’s 2025 report holds 2025 data. Southlake’s water page also lists a newer Southlake report that this post does not use.
| Reading | Southlake 2023 report | Fort Worth 2025 report |
|---|---|---|
| Total hardness as CaCO3 | 100 to 171 ppm | 108 to 150 ppm |
| Hardness in grains | 6 to 10 grains per gallon | 6 to 9 grains per gallon |
| pH | 8.1 to 8.5 | 7.8 to 8.5 |
| Total alkalinity as CaCO3 | 90.4 to 144 ppm | 99.7 to 124 ppm |
| Total dissolved solids | 161 to 278 ppm | 182 to 244 ppm |
| Calcium | 33.6 to 51.9 ppm | 37.6 to 48.1 ppm |
Both reports give ranges, not one number. The tap water at your house depends on the day and on which part of the system serves you.
Why does a tap water range matter for a pool?
Water leaves a pool through evaporation and the minerals stay behind. Each top-off adds more. So a pool can drift far from the tap numbers in a season.
Three readings matter most when you fill:
- Calcium hardness: the mineral level that affects plaster and equipment.
- pH: both reports show tap water pH of 7.8 or higher, so a pH check after a fill makes sense.
- Total alkalinity: it steadies pH, so it moves with every fill.
The water balance of your pool is the full picture. Our pool water chemistry chart lists each reading and why it matters.
How do I read the ranges?
Each range runs from the lowest to the highest result in that report year. Southlake’s report lists 2022 data and Fort Worth’s lists 2025 data, so the two ranges are not from the same year. They still agree on the main point: Fort Worth water is in the same band of roughly 6 to 10 grains per gallon. A single test at your tap can land anywhere inside that range.
What should Southlake pool owners do with this?
Treat the reports as a guide and your pool test as the answer. Keep a short routine:
| When | What to do |
|---|---|
| Before you top off | Test calcium hardness, pH and alkalinity |
| After a large fill | Test again once the water has mixed |
| Each season | Compare your readings with the last season |
| If you see crust or rough plaster | Run a full test and ask a pro |
Marina Pool Services weekly service covers water balance, including calcium hardness and conditioner, and empties baskets and backwashes filters as needed. See the weekly pool service page for details.
Where can I read the reports?
Southlake posts its reports on the city water quality page. Fort Worth posts its 2025 report on the Fort Worth water quality page. Open the secondary constituents table, which holds hardness, pH and alkalinity.
Reports change each year, so check the date on the version you read. For wider advice, read our North Texas pool care guide or see our Southlake service page.
Next step
If you want a second set of eyes on your water balance, see our pool maintenance services. Call (817) 896-1120 or use the quote form at /contact.
Frequently asked questions
Where does Southlake get its water?
Southlake's 2023 water quality report says the city gets all of its water from the City of Fort Worth. Fort Worth draws from Lake Worth, Eagle Mountain Lake, Lake Bridgeport, Richland Chambers Reservoir, Cedar Creek Reservoir and the Clear Fork Trinity River.
How hard is Southlake tap water?
Southlake's 2023 report lists total hardness of 100 to 171 ppm, or 6 to 10 grains per gallon. Fort Worth's 2025 report lists 108 to 150 ppm, or 6 to 9 grains per gallon. The range is wide because the number changes over the year.
Can I use the city report as my pool test?
No. The report describes water in the city system. A pool changes as water evaporates and minerals stay behind. Test the pool water for calcium hardness, pH and alkalinity, and use the city report only as a reference for what you add when you fill.
Pool terms on this page
Sources
- City of Southlake: 2023 Water Quality Report
- City of Southlake: Water Quality
- City of Fort Worth: Water Quality Reports (2025 report)
Written by Marina Pool Services and checked against the sources above on October 21, 2026. City rules and product guidance change, so check the linked page before you act. Follow product labels for any pool chemical.
