This is at my mom's house, an hour away. The valve in the first photo has a slow drip and I will be replacing it. The other photo (a union?) is one of a few spots that look similar but are not currently leaking.

I know the green is oxidation. How big of a concern it is that it will leak? What about all the white flaky stuff?

Should I just replace all the valves that are solid green and/or white? Should I try to clean them off and then see what they look like first?

I'm trying to prevent an emergency trip there for another leak but also not do needless work. She is on a private well.

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The green stuff is cupric chloride, a byproduct of corrosion of the valve body or possible copper leachate in the water. Either way, it's typical of water leakage where the water is of low pH.

The white stuff (sometimes feels fibrous like cotton candy) is just efflorescence. This is from dissolved minerals in the water precipitating out as the leak drips, then dries and deposits miniscule quantities of calcium, sodium, etc on the valve body. You often see this where residual flux was left on a pipe and over time, condensation or outright leakage causes these buildups. It's always more pronounced at joints between dissimilar metals (due to galvanism).

Wearing gloves, as copper chlorides are toxic, you can remove them with full strength vinegar or dilute muriatic acid, lemon juice or even more flux and a bristle brush. Once it's cleaned up, repair the leak or tighten the packing gland on the valve stem. Then when all done, just liberally apply a paste of baking soda and water. It will neutralize the flux and retard further reaction (if it's condensation related). It would be wise to have your water tested for acidity. If you have highly acidic water, it can cause the same problem or just dissolve pipes outright.

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    hey - cupric chloride is green, cuprous is white. and cuprous is not soluble in water. ergo, the green goo is cupric. dont edit my post unless you know what you are talking about – personal privacy advocate Mar 6 '16 at 23:52
  • PPA, for future reference, @isherwood won't see your message unless you use the at-sign with his name. Since I just did so here, maybe he'll come back and read this. – chue x Mar 6 '16 at 23:59
  • OP here, thanks! So the valve I'm replacing, don't need to clean or repair it. What about the union? Clean it off and it might be ok, or better safe thank sorry and replace? – user20127 Mar 7 '16 at 0:48
  • you will need to repair it or the union if they are leaking, but if not, just clean and apply baking soda. – personal privacy advocate Mar 7 '16 at 4:01
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    i could honestly care less if anyone wants to edit my posts for format or grammar. however, if you feel the need to do so, by all means proceed. changing content though should be avoided unless you are sure what you are adding is correct. i do however appreciate that anyone can make a mistake. perhaps the best way to put it is that mistakes in chemistry related issues can sometimes lead to disastrous results, so let all make sure our facts are straight before we offer input - to questions or to answers. – personal privacy advocate Mar 7 '16 at 17:00

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