Is it safe to swim in a pool with high or low pH?

No. Ideally, pool pH should be 7.4 to 7.6, but 7.2 to 7.8 is okay if you’re careful. High pH over 8.0 makes chlorine less effective and can cause skin rashes and eye irritation. Low pH under 7.0 is worse — it eats at metal fixtures and irritates skin and eyes. Adjust pH before swimming.