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Current IssueSeptember 04, 2015
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Ask The Expert: Three Questions on Corrosivity: Reluctant Guinea Pigs
Question: Our homeowners association along with the Department of Environmental Quality wants to put stannous chloride in our water to solve the corrosive water problem. I am against any more chemicals added to water. I think aeration would be safer. What other alternatives would you suggest for treating the water, and if we settle on the stannous chloride, will an RO water system filter it out of our drinking water? Have you any tests on the effects of stannous chloride on people? We are going to be the guinea pigs if the association agrees to it. Any info you could send my way would be greatly appreciated.

Frankie Avalon Wolfe, Ph.D., M.H.H., R.N.C.P. -- Boise, Idaho 

Answer:  Answer: First of all, stannous fluoride is often used in toothpaste (as well as other salts containing tin) and is a proven aid to preventing tooth decay. Second, tin (stannous means tin), is generally considered to be non-toxic and, before it became too expensive, was used to make "tin" cans. While the two are not the same compound, a few parts per million (ppm) of stannous chloride added to your water isn't likely to do you any harm. I haven't heard of anyone using this chemical for corrosion control, and it seems like there may be less expensive alternatives. Yes, an RO system will remove most of the stannous chloride that's added, along with other salts and minerals. A carbon prefilter provides sufficient prefiltration of suspended solids for most applications. A carbon postfilter should also be used, and you can either get a unit with the postfilter between the membrane element and the storage tank or between the storage tank and the faucet-you don't need them in both places. One thing for certain is that aeration, except in very unusual circumstances, isn't going to make a water less corrosive, except inasmuch as it reduces hydrogen sulfide (H2S) which can be corrosive. Without knowing more about your water supply and the analysis, there's no reason to second guess what your environmental engineers are telling you.

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