Your test shows 7.8, or 8.0, and the kids want to swim. Here is what those numbers mean.
The short answer: 7.8 is inside the CDC's range for home pools (7.0 to 7.8), so you can swim if free chlorine is in range too: at least 1 ppm, or 2 ppm with stabilizer (CDC). Above 7.8 you are outside the range, and above 8.0 the CDC says chlorine kills germs less well: bring pH back to 7.8 or lower before swimming (our advice).
Part of: Pool pH and Alkalinity: How They Work Together, our overview of every pH and alkalinity fix.
What 7.8, 8.0 and higher mean
| pH | What the sources say |
|---|---|
| 7.0 to 7.8 | Inside the CDC range: it "best balances killing germs", pipe life and swimmers' comfort. |
| 7.4 to 7.6 | Taylor Technologies' target: the middle of the range. |
| Above 7.8 | Outside the CDC range. |
| Above 8.0 | CDC: chlorine's ability to kill germs decreases, especially here. Better Health Channel: swimmers are at risk of skin rashes above 8. |
What to do before the next swim
- Test free chlorine too: the CDC's minimum is 1 ppm (2 ppm with stabilizer).
- Check total alkalinity: high alkalinity is why pH keeps coming back (why pH keeps rising).
- Lower pH with acid: how to lower ph in a pool.
- Keep people out of the pool while the acid mixes, and retest. The Sunnyside muriatic acid label says to keep swimmers out until the acid is thoroughly mixed in and pH is between 7.2 and 7.6.
As an Amazon Associate we earn from qualifying purchases. We have not tested these products.
Test kit A test kit that reads pH and total alkalinityEvery step on this page starts and ends with a test. A drop-based (liquid) kit or test strips both work; follow the kit's own instructions.
FAQ
Is 7.8 pH too high for a pool?
Not by the CDC's range, which ends at 7.8. Taylor Technologies aims lower, at 7.4 to 7.6, so 7.8 is a good moment to plan an acid dose (our advice).
Is high pH dangerous?
The main concern is weaker chlorine (CDC) and skin rashes above 8 (Better Health Channel), not an instant danger from the pH itself (our reading of these sources).
What should I do at pH 8.0 or above?
Lower it before swimming. The amount of acid depends on the product and your volume: see muriatic acid for pools and how to lower ph in a pool.
Sources
- CDC: Home pool and hot tub water treatment and testing (pH 7.0 to 7.8, chlorine above 8.0, chlorine minimums)
- Better Health Channel (Victoria State Government): Swimming pools, water quality (skin rashes above pH 8)
- Taylor Technologies: LSI calculator (target 7.4 to 7.6)
- Sunnyside Muriatic Acid label, 31.45% hydrochloric acid (keep swimmers out until mixed, pH 7.2 to 7.6)
Sources read on November 4, 2026. Product labels change: the label on the product you buy always wins.
