Hey guys, this is Rudy Stankowitz with Aquatic Facility Training and Consultants and the Talking Pools Podcast, and we have a copper stain in this pool. This is cupric oxide, and it’s from a degradation reaction between copper and chlorine. Cupric oxide is insoluble and precipitates out, leaving this black blotchy stain. It cannot be brushed off but may go away on its own. Still, that could take up to 12 hours when it doesn’t go away at all.
Before you try this I need you to understand that the longer a stain is in place the less likely it is it can be removed.
Regardless, I want to remove it now, so I do not have to worry about it. Oddly, I do not have aluminum sulfate on hand. So, I took a trip to the local supermarket. In the spice aisle, I grabbed a container of McCormick® alum.
I will try to sprinkle the alum directly over the spot to do my best. I only have one place in the pool, and there’s no reason to add a large quantity to treat the entire swimming pool. I think the amount in this container will be plenty for what I am looking to do.
Alum is aluminum sulfate (used in the manufacture of pickles, cosmetics, water treatment, and more) and is roughly 15% aluminum. In chemistry, if we look at the reactivity series of metals (the ability of one metal to displace another), we can see that aluminum is more reactive than copper. So, by sprinkling the alum over the copper stain, the aluminum in the spice will displace the copper and lift the stain.
In sprinkling it over the area, it looks like I got it pretty much over the top of it. I’ll let it sit for a minute, and it shouldn’t take long. You can see the flock forming that aluminum hydroxide schmutz associated with using alum as a flock. You can still see the stain beneath the alum, and it’s quick but not instantaneous.
Grocery Store Spice Aisle Pool Hack
The reaction you see in the video is real-time, so it should give you a good idea of how long this process takes. We can see that it’s lightening up quite a bit. Still, it’s hard to tell what’s happening beneath that aluminum hydroxide cloud. I only used a small amount of alum, so that’ll go away on its own, but I’m going to hit it with a brush so we can see what we have left of the stain. It looks like we are pretty much gone.
If I don’t want that stain to come back, there is a second part to this. I’ll need to add a sequestering agent. A sequestering agent keeps metals in the water in the solution, so they don’t precipitate and cause staining. I like to use natural chemistry products, stain and scale control, a highly concentrated product from their Pro Series line.
We’ve just pulled metals from the surface of this pool and do not want them to redeposit, leaving a stain in the same spot or some other area. The initial dose is a quart to 10,000 gallons of pool water. It is super concentrated, and a quart for 10K gallons may sound like a little bit, but in the months to follow, the maintenance dose is only 5 ounces per 10,000 gallons of pool water. You really don’t use that much of this product going forward.
In this hack, we used just a little bit of McCormick®spice from my grocery store spice aisle to remove the stain and added Natural Chemistry stain and scale Control (Pro Series) to keep it from coming back.