I Found a Crusty White Powder on My Water Shutoff Valves—Should I Be Worried?

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# I Found a Crusty White Powder on My Water Shutoff Valves—Should I Be Worried?

You open the cabinet under the sink or glance at the water shutoff valve near your toilet or water heater—and there it is: **a crusty white powder** coating the valve, pipe joint, or surrounding metal.

Your first thought might be:

* *Is this mold?*
* *Is my pipe leaking?*
* *Is something corroding?*
* *Is this dangerous?*

The short answer: **usually no, but it deserves attention**.

That chalky white buildup is very common in homes, especially older ones, and in most cases it’s a sign of **mineral deposits or corrosion**, not an immediate emergency. Still, ignoring it completely isn’t a great idea either.

Let’s walk through **what it is, why it appears, when it’s harmless, and when you should take action**.

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## What Is That Crusty White Powder?
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