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I used cupric sulfate as an algaecide in my swimming pool for a while without problem. I was adding a very small quantity of it (one teaspoon when the season start and 1/4 teaspoon whenever I add water.) However, a "swimming pool expert" told me I should not, that it is dangerous, and various others claim (Obviously, he wanted to sell me his own algaecide). I had many problem this year to keep my swimming pool clear of algae, So I'm considering returning back to cupric sulfate.

So, I made my own search and this use copper sulfate seam quite controversial:

Does someone has an objective notice for that?

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3 Answers 3

up vote 3 down vote accepted

As with any chemical, it depends on the amount. Overdose and you'll not be very well off. Check the volume of your pool and keep it below 1ppm.

The EPA limit for copper sulfate in drinking water is 1 ppm. This limit has been set to prevent a disagreeable taste from copper in drinking water, as well as to provide adequate protection from toxicity.

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Will it work as an algaecide at those levels? –  Oddthinking Sep 8 '11 at 0:31
apparently 0.25tsp / swimming pool worked for him. Olympic sized pools are 2,5000m^3 so 0.25tsp would be about 0.05ppm, which is below the legal limit. It depends on his swimming pool volume, which he doesn't specify. –  user4686 Sep 8 '11 at 3:06
I got a 30 000 liters pool. So, if I calculate correctly, the 1ppm limit is about 30 gram (6 teaspoon), right? –  DavRob60 Sep 8 '11 at 12:11
Remember, this isn't drinking water. The limit for chlorine in drinking water is 4ppm, but I've been in many a pool with much higher levels than that. Still, you'll want to keep it (the level of copper sulfate) around .5ppm, otherwise peoples hair will start turning green. –  Satanicpuppy Sep 8 '11 at 14:35
@Satanicpuppy 0.5ppm copper will turn hair green? Sounds like time to ask a question... –  Nick T Apr 26 '12 at 19:53

Health Canada said it's OK, but they don't say anything about the recommended concentrations except to refer to the label directions :

Health Canada has found that using copper sulphate-based algicides in swimming pools presents no significant danger to bathers. When used according to the label directions, copper sulphate algicide should not cause skin irritation for bathers. However, label directions should be carefully followed when handling undiluted copper sulphate-based products to reduce the potential for skin irritation.

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I know people who have used Copper Sulfate for years and zero problems. 1 tsp put in the scimmer for a 22 foot round pool then a few hours later back wash the filter. I never asked why to back wash the filter unless it was to remove the dead algae. He then adds 1/4 to 1/2 a couple times a year if the weather is real hot and the pool used by lots of people.The total cost to keep his pool clean is next to nothing a year.

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Welcome to Skeptics! Please provide some references to support your claims. –  Larian LeQuella Sep 14 '13 at 16:19

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