Low pH eats your heater from the inside.

Low pH water slowly dissolves the copper heat exchanger in a gas pool heater, and once that metal is gone, you can’t reverse it.

pH below 7.0 means the water is acidic, and acidic water wants to dissolve copper. The heat exchanger is basically a bunch of copper tubes with water running through them. Over time, low pH strips metal off the inside surfaces, making the walls thinner and pitted until eventually you get a pinhole leak. It’s not a coating problem — the metal is literally being carried away in the water.

Could you catch it early? Yes, if you notice pitting or just know your pH has been drifting low, you can fix the water chemistry and stop the corrosion from getting worse. That’s worth doing. But the copper that’s already gone doesn’t grow back. If the exchanger is leaking, no chemical treatment is going to patch it. You’re looking at a replacement, and on most gas heaters that’s a big chunk of