Pool school
What your pool water readings tell you
Sullivan’s Pool Service uses water tests to guide pool care. For home pools, CDC recommends pH 7.0–7.8 and free chlorine of at least 1 ppm, or at least 2 ppm when cyanuric acid or stabilized chlorine is used. Test chlorine and pH at least twice daily, including between weekly visits. Equipment-specific water balance and fill-water quality need separate attention.
Keep routine tests in the plan
CDC recommends testing chlorine and pH at least twice a day, with more frequent checks during heavy use. The weekly visit balances the water; quick checks between visits catch a change early. Agree who will test between visits and keep the test kit’s instructions available. Record the date, readings and any treatment rather than relying on water appearance or smell.
CDC recommends a DPD kit for accurate free-chlorine testing. It also warns that chlorine above 10 ppm can bleach a test result and make the reading appear low or zero. Follow the test manufacturer’s instructions; an unexpected result is a reason to check the test method before making an unsupported dosing decision.
CDC guidance for home pools
| Reading | Guidance | Context |
|---|---|---|
| Free chlorine, home pool | At least 1 ppm | CDC’s recommendation when cyanuric acid or stabilized chlorine is not used. |
| Free chlorine with cyanuric acid | At least 2 ppm | CDC’s minimum for home pools using cyanuric acid or a stabilized chlorine product. |
| pH, home pool | 7.0–7.8 | CDC’s recommended range; pH affects how well chlorine disinfects. |
| Other balance readings | Check the system instructions | Calcium hardness, alkalinity and other equipment requirements need the pool surface, device manuals and actual test results. |
Source: CDC home-pool treatment and testing. These recommendations do not replace chemical labels, equipment manuals or public-pool operating rules. Hot tubs have different disinfectant guidance; see spa and hot-tub care.
Disinfection and water balance answer different questions
Chlorine and pH checks address disinfection guidance. Other measurements are needed to assess compatibility with a pool surface or a particular piece of equipment. A water-balance calculation does not demonstrate that disinfectant is adequate, and a reading inside a generic table is not a complete assessment of the system.
Have the surface and equipment information available when discussing targets. Use the manufacturer’s requirements for that installation. Do not apply an anonymous “industry standard” calcium, alkalinity or stabilizer range to every pool, or assume that adding more of a product is the answer to an unexpected reading.
Test the water you actually add
Austin Water identifies Lake Austin and Lake Travis on the Lower Colorado River as its source. Its water-quality reports contain measured results, including hardness. Its quarterly summary for the second quarter of 2026 reported total hardness of 76 to 77 mg/L as CaCO3 in the finished water leaving its three treatment plants. Those figures provide context about the utility’s supply; they do not establish the composition of every customer’s pool.
Source: Austin Water, Water Quality Summary, 2nd Quarter 2026 (samples April 1 to June 30, 2026), finished water at the Davis, Ullrich and Handcox plant taps. Figures as of .
The wider service area includes different water suppliers. Check the supplier for the property and test the actual fill water when comparing it with the pool. Regional limestone, a soil survey and a street address are not substitutes for that measurement.
Evaporation is not the same as splash-out
EPA’s pool guidance notes that pool water continually builds up dissolved solids, in the form of mineral salts and treatment chemicals, which must be managed to prevent scale and corrosion. Splash-out removes mixed pool water, carrying dissolved material with it. Replacing either loss changes the pool according to what was lost and what is in the incoming water, so hardness can move either way.
EPA also describes reverse osmosis and nanofiltration for removing dissolved minerals from pool water. Water replacement is therefore not the only mineral-removal method. It is not one of the services we list. Any proposal needs to consider suitability, water quality, the structure and applicable discharge rules. Do not drain a pool based solely on a general article or a single test.
Use changes as information
Send recent readings, product names and dates, water-loss or refill history, and any equipment symptoms when requesting help. Tell us what changed and when, and we assess it on the property.
Water testing and balancing is part of our service scope. Read about waterline deposits, summer care, spa symptoms and comparing equipment upgrades. The notes archive collects these guides.
Further technical source: EPA WaterSense at Work: commercial pools and spas, particularly its discussion of water loss and dissolved-mineral treatment.
Questions about the readings
How often should I test between weekly pool visits?
CDC recommends chlorine and pH tests at least twice daily and more often during heavy use. The weekly visit balances the water; these quick checks between visits catch a change early. Follow the test manufacturer’s instructions, record the results and arrange who will monitor the pool between visits.
Can a city water report tell me what my pool needs?
A utility report describes the water the utility tested. Your pool has its own treatment, use and refill history, and properties in the wider service area can have different suppliers. Test the pool and its actual fill water; do not infer their chemistry from a ZIP code or soil map.
Is replacing water the only way to reduce dissolved minerals?
No. EPA describes reverse osmosis and nanofiltration as ways to remove dissolved minerals from pool water and return treated water. Water replacement is another option when the replacement water has less of the constituent being reduced. Suitability, structural safety and discharge requirements need assessment; this is not an instruction to drain the pool.
Does a salt system remove the need to test chlorine?
No. A salt chlorine generator produces chlorine; it does not make the pool chlorine-free. Routine disinfectant and pH checks still matter. Follow the generator manual and applicable chemical labels as well as the public-health guidance for your type of pool.
Tell us about your pool
Tell us your service location and whether you need weekly care, help with equipment, or a one-time service. Call or send the quote form. We’ll confirm availability and the next step for your pool. Repairs and other separately quoted work are discussed before approval.