Filling a Pool? Look Up Your City’s Tap Water Numbers First
Every pool starts as tap water — and tap water arrives with its own hardness, alkalinity, and pH, set by your utility, not your pool store. This lookup shows the published fill-water chemistry for 27 sun-belt metros, from each utility’s own water-quality report, so you know what day one looks like before the hose goes in.
All metros
| Metro | Total hardness (mg/L) | Alkalinity (mg/L) | pH |
|---|---|---|---|
| Chandler, AZ | 173-288 | 111-168 | 7.2-8.1 |
| Glendale, AZ | 153-309 (typically ~229) | 89-207 (typically ~138) | 7.2-8.2 |
| Mesa, AZ | 205-376 | not published | 6.6-8.51 |
| Phoenix, AZ | 172-302 | 121-167 | 6.6-8.8 |
| Scottsdale, AZ | 215-290 | 108-220 | 7.3-8.2 |
| Tucson, AZ | 78.3-340 (typically ~209) | not published | 7.09-8.05 |
| Anaheim, CA | 162-431 | 93-222 | 7.5-8.5 |
| Bakersfield, CA | 38.6-380 (typically ~105) | 39-140 (typically ~91) | 5.7-8.9 |
| Fresno, CA | 87-150 (typically ~129) | not published | not published |
| Los Angeles, CA | 78-280 | 86-124 | 7-8.7 |
| Riverside, CA | 180-210 (typically ~197) | 140-170 (typically ~157) | 7.4-8.1 |
| Sacramento, CA | 15-154 (typically ~83) | 27-150 (typically ~100) | not published |
| San Diego, CA | 54.4-285 | 46-155 | 7.4-9 |
| Jacksonville, FL | 120-372 | not published | not published |
| Orlando, FL | ~129 | not published | not published |
| St. Petersburg, FL | ~158 | ~125 | 8.2 |
| Tampa, FL | ~211 | not published | 7.88 |
| Charlotte, NC | 27-35 (typically ~32) | 17-25 (typically ~21) | 7.4-9.5 |
| Henderson, NV | ~304 | not published | not published |
| Las Vegas, NV | ~280 | ~137 | 7.8 |
| Arlington, TX | 80.4-110 (typically ~94) | 73-98.9 (typically ~85.2) | 7.82-8.38 |
| Austin, TX | 70-126 (typically ~93) | 51-60 (typically ~54) | 9.65-9.74 |
| Corpus Christi, TX | 158-236 (typically ~170) | 116-151 (typically ~122) | 7.33-8 |
| El Paso, TX | 63-236 (typically ~175) | 24.5-133 | 7.3-8.1 |
| Fort Worth, TX | 108-150 (typically ~129) | 99.7-124 (typically ~112) | 7.8-8.5 |
| Houston, TX | 43.4-137 (typically ~110) | not published | 7.4-9 |
| San Antonio, TX | 257-342 (typically ~300) | not published | not published |
How to read these numbers
Utilities publish TOTAL hardness; pool target ranges (calcium hardness 200-400 ppm, alkalinity 80-120 ppm, pH 7.2-7.8) are for what a pool test kit reads — test after filling rather than assuming. Values are system-wide figures from each utility’s latest published report (report year shown on every city page); your service zone and season can vary. Stabilizer (cyanuric acid) is zero in all municipal water.
“Which way this water pushes a pool”
Warm water is never neutral about calcium: it either deposits calcium carbonate as scale or dissolves it out of plaster, grout and heater parts. The pool trade reads that direction with the Langelier saturation index, which combines pH, calcium hardness, alkalinity, total dissolved solids and temperature into a single signed number — negative is aggressive, positive is scale-forming, and -0.3 to +0.5 is the balanced band published by the Pool & Hot Tub Alliance. (Some calculators still use +0.3 as the upper value; PHTA calls that figure outdated.) Each city page runs that utility’s own published figures through it at a typical 84 F pool temperature.
Two honest limits on every one of those figures. First, utilities publish TOTAL hardness while the index wants the CALCIUM fraction of it, and the index rises with hardness — so what each city page reports is a CEILING, and the true reading sits at or below it. That asymmetry is usable: where even the ceiling is negative, the water is aggressive beyond doubt. Second, this is FILL water, not pool water. It is the direction the water arrives pointing, before your pool, its surface and your chemicals have any say.
“The top-off arithmetic”
Evaporation removes pure water and leaves every dissolved mineral behind, so the make-up water you add arrives carrying your city’s hardness all over again. Calcium does not evaporate; in a pool it only accumulates. Replacing one full pool volume through top-off therefore adds roughly the fill water’s own hardness a second time, and each city page reports how many pool volumes of make-up water that allows before hardness reaches the 400 ppm ceiling most residential pools work under. It is an evaporation-only bound and deliberately the fastest case — splash-out, backwash and rain all dilute — so read it as a ceiling on the rate, never as a schedule.
No dosing advice lives on these pages: amounts depend on your pool volume and your product’s strength — product labels govern. Never mix pool chemicals.
Picking a cleaner for that water
Hard fill water and a robot that is not rated for your pool are two different problems, and only one of them is fixable with chemistry. These compare what the manufacturers actually publish:
- Which Wybot Pool Robots Are Rated for Above-Ground Pools (Maker Specs, All Models)
- Beatbot vs Dolphin by Pool Type: What Each Line Is Actually Rated For
Built 2026-08-15 from utility-published reports. This is an experimental section; sources and report years are cited on every city page.