Pool turned green from copper and a chlorine shock

I got a text from a customer in the Northeast that just finished plastering a pool the week before. The text had a picture in it of a green pool, and it read:

"Pool we plastered last Thursday. Water immediately turned yellow when we added 2.5 gallons of liquid chlorine, after we added 1 quart of algaecide. Any thoughts?"

copper green pool

My first thought was algae when I saw the color of the pool. But that thought lasted all of about 15 seconds. This was a brand new pool.  The next most plausible explanation was the pool turned green from copper. Why? Because we have encountered copper before and it was the reason for a pool turning green.

The pool turned green from copper, not algae

Statue of Liberty, oxidized copper, copper oxidation, green copper

Copper, when oxidized, turns green. Think of the Statue of Liberty. It is made of copper, and has turned green over time through oxidation. What accelerates oxidation? Oxidizers like chlorine. Copper was making some sense, except that the customer started up his pool using our SC-1000 chelating agent. In that case, copper should have been isolated and not falling out of solution... so this wasn't making complete sense.

So I read the text again, more carefully. "Water immediately turned yellow when we added 2.5 gallons of liquid chlorine after we added 1 quart of algaecide..." What was in the algaecide?

Sure enough, the algaecide product was copper-based. Normally SC-1000 will neutralize a copper-based algaecide, but in this case, the algaecide was followed up with 2.5 gallons of liquid chlorine. I know that because I spoke with the customer on the phone about it. The chlorine was poured in moments after the algaecide. Perhaps chlorine oxidized it faster than SC-1000 could chelate it.

We asked for a water test to figure out the copper level, because the next picture he texted me was this:

copper water, green pool
The homeowner was filling their pool with well water from their property. This is their water, straight from the tap.

The homeowner started filling their pool with well water. Most of the pool was actually filled by a water truck from a local municipal water source, but this first initial amount of water clearly had a lot of metal in it. I mean...look at it. We did the math and estimate that when the well water hose was shut off and the truck took over, 1/36th of the pool was filled with the green water you see above. Could that have been enough copper to cause a problem?

Copper-based algaecide was oxidized by the chlorine shock, and turned the entire pool green

Between the fill water and the copper-based algaecide, there was enough copper to react with chlorine immediately. The reaction happened before the customer's eyes, which I'm sure is crazy to watch. It's also a crisis in the moment. If you have never been in that situation, can you imagine being the pool company that just turned a brand new pool green from copper? Because it got more green as the day went on...

copper green pool, green from copper

Fixing the problem

Our SC-1000 chelates metals, but it does not remove metals from the water. Such products do exist, however.

The customer combined a metal removal product with more SC-1000. It was a blitz strategy to control as much copper as possible, and fortunately, it worked out!  Here's the pool after 48 hours and some backwashing:


green pool, pool turned green from copper
Green no longer. Removing the copper was critical to restoring clarity to this homeowner's brand new pool.

This is a valuable lesson that hopefully will never happen to you. But if it does, consider the consequences of oxidizing copper (it turns green!). There are metal test kits out there, and it would be wise to test your tap water for metal content. The more you know, the less surprises happen. If you know you have metal in your source water, consider using a MetalTrap filter when filling your pool.

Normally SC-1000 can handle metals just fine, but there was no time to stop the oxidation of that copper-based algaecide. The chlorine shock that immediately followed it set off the reaction, and the pool turned green from copper. Who would've thought? If you have this problem or know someone who does, feel free to contact us if you need help.

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