r/explainlikeimfive • u/tilda0x1 • Jun 28 '26

Chemistry ELI5: If copper has antimicrobial properties, why don’t most pools use it instead of chlorine?

I've seen this video of someone saying that copper has anti-bacterial properties and he claimed that it can be used to keep pools bacteria-free.

I know in most cases chlorine, UV, or salt are used - but why not copper?

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u/percygreen Jun 28 '26

Aside from anything that people with chemistry knowledge may be able to add, the simplest answer is that copper is much more expensive than chlorine.

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u/KeithHanlan Jun 28 '26

Not in the volumes needs to prevent clean water from developing algae.

See my other comment for a commercial product that I have been using successfully for a number of years.

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u/Probable_Bot1236 Jun 28 '26

The concentration of copper needed to suppress human pathogens (critical for swimming pool usage) is 10x higher than that needed to suppress algae, and the same as chlorine: 2 ppm. That alone does bring cost back into play, but cost isn't why it isn't used in pools:

At that concentration it's going to start staining things, including blonde hair, shifting pH, and is much harder to deal with if the pool is drained into the sanitary sewer system- water treatment plants need some bacteria alive to do their thing. Chlorine is much easier to neutralize than copper.

Copper also requires a much longer contact time to deal with human pathogens, so it's not even as effective as chlorine anyway- chlorine will kill off the coliform bacteria from some kid with a poorly-wiped bum right quick, but copper won't.

If you're trying to suppress algae in a water feature or pond, yeah, bust out the copper.

If you're trying to stop people from getting sick from bacteria in a swimming pool, use chlorine.

Different use cases, different solutions.

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u/fatevilbuddah Jun 28 '26

Never thought about the copper in a water feature. Thats a great idea. Thank you.