I have two toilets in my house. One toilet has green streaks, and one does not. I can't figure out what is causing these streaks unless it is calcium deposits. If it is calcium, what can I use to get rid of it? Why does one toilet have it and the other doesn't?

I have two toilets in my house. One toilet has green streaks, and one does not. I can't figure out what is causing these streaks unless it is calcium deposits. If it is calcium, what can I use to get rid of it? Why does one toilet have it and the other doesn't?

— Louis J., Phoenix

OK, Louis, since there's no such thing as a streak specialist, we turned to water treatment specialist Rick Davis of Complete Water Solutions to explain the mystery green lines.

Davis confirmed what a Google search told us — your green streaks are not calcium deposits, which result in white spots, but rather the effect of acidic well water or old, copper plumbing.

Well water tends to have a low pH and/or more iron than city water, Davis said. The extra acidity corrodes the pipes, resulting in a bluish green residue in the toilet bowl.

However, since your other toilet is streak-free, copper plumbing is the most likely suspect in your case.

"Newer homes are plumbed with PEX plumbing, which is a plastic, but in older homes, plumbing is galvanized or copper," Davis explained.

"Copper will deteriorate, especially if the water is acidic, to where it's going to create that blue-green look."

Davis said he doesn't know of any secret solution to get rid of the unsightly stains. And, since bleach, the duct tape of solutions, is an oxidizer, it could make things worse.

Instead, Davis suggested having a water treatment specialist or plumber look at it to determine the cause. There are pH-enhancing filters you can buy to neutralize the water, and copper pipes can be replaced.

Of course, if either of those options is too costly, you could always try some of the home remedies found on various forums online. Most involve some salt, vinegar, a pumice stone and elbow grease.

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