Our pool hasn't been opened in 4 years. We are finally in the process of resurrecting it from the dead, and have spent a lot of elbow grease (and tears) to get it to the point its currently at. Last night the water was a blueish turquoise, but was still opaque and very hazy (still couldn't see to the bottom of the shallow end). I added 5 gallons of liquid chlorine ("shock") and instantly the water turned green. I read up on it and it looks like if there is a lot of metal in the water, such as iron, chlorine has this affect.

However, all the articles/forums/info I find on this problem don't really have any good posted solutions, so I figured I'd ask:

What's the solution here? Is there a pool chemical I can buy that will help "get rid of" these metals and turn my water back to blue-ish haze?

  • 1
    So are we just talking mineral content in the water?
    – James
    Commented Jul 14, 2014 at 16:37
  • 1
    CuLator® Metal Eliminator and Stain Preventer. I am not affiliated with this product, and do not endorse or recommend it's use. It's simply the first product I found when searching "remove metal from pool water".
    – Tester101
    Commented Jul 14, 2014 at 16:40
  • Thanks @James (+1) - I guess, if heavy metals such as iron are minerals (not sure if they are). Like what Tester101 posted.
    – bfodder
    Commented Jul 14, 2014 at 16:42
  • Sounds like copper or nickel, not iron. Do they sell ion exchange cartridges for pools? -Sometimes called water softeners. A few hours pumping through one of those should clear up your divalent metal ion problem. Commented Feb 12, 2016 at 19:31

6 Answers 6


There are several independent variables to manage in a swimming pool or hot tub:

  • pH balance
  • halogen balance
  • calcium hardness
  • total dissolved solids

Nearly everyone is aware of pH balance, but what most people don't seem to understand is that pH can swing wildly unless total alkalinity is increased sufficiently to provide an "inertial buffer" with total acid. Then moderate changes in chlorine or bromine content do not affect the pH so much.

The other thing most people are familiar with is chlorine. Bromine can be used instead and is just as effective at killing bacteria but with possibly less skin and eye irritation. At my pool store, they are priced the same. The standard home pool test kit measures both pH and "free chlorine equivalent".

Calcium should be added to soft water to prevent the water from attacking and rusting metal components of the pool and filter system. This is a particular problem for areas such as the Pacific Northwest which has naturally soft water. Most well-based systems will have some calcium, but if it is not adequate, some supplementation is cheap insurance for minimal maintenance.

See this for a detailed and reasonably approachable roundup of pool chemistry. Note that everything affects everything else, so reading it twice is probably necessary to gain full insight.

In my experience, green water could be caused by either iron or copper in the water, like someone's lost jeans rivet inside the drain. A chemical to precipitate and flocculate the metals need be done only when it is a problem.

If the history of the water is uncertain or a lot of junk has entered the pool water since it was last filled, there is no substitute for draining and refilling it. This reduces the total chemical load to the minimum and will make it simple to balance. To maintain that simplicity, insist that all pool users shower before entering to remove sunscreen, oils, perfumes, deodorants, etc.


Get ready to buy some chemicals and clean your filter. You need a chelating agent (for pools often sold as "Metal Free") to bind the metals. Adding a clarifier will help coagulate that plus the other hazy junk so they form particles large enough to get stuck in your filter.


This has happened to my pool many times too. It's the metal particles in the water reacting with chlorine indeed. I use aluminum sulfate, which you can buy in any pool shop in bags of ~20 kg. Just sprinkle evenly before night, depending of the size of your pool. It will react with metal particles and form a sort of dust, which will fall to the bottom of the pool. The next day VERY CAREFULLY hoover your pool. My sand filter does not fully stop the dust, and some of it comes back to the pool. So I just swich it to 'waste' and dirty water with dust in it goes out. After that, water is super clean back. Just make sure during the cleaning you dont make too much movement in the water, as the sulfate dust lifts very easly and takes some time to fall down again. Good Luck!


Sorry I am late to this post. No doubt it is solved now.

Adding sodium hypochlorite to a water body that contains iron will result in a dark green appearance. Simply leave the filter running and add more chlorine. This dark green will suddenly vanish usually the next day provided chlorine is kept up.

Used to be common problem in pools with steel pipe work back when I started in this industry.

  • Welcome to Home Improvement. This is, essentially, the same as this answer that received a down vote and a comment asking for how much calcium hypercholrite. If you would edit to indicate a quantity per gallon of water, I'm sure this would be very useful.
    – FreeMan
    Commented Sep 16, 2022 at 11:48
  • Calcium Hypochlorite I dont think works the same. I am unsure. I only ever saw this when converting old pools from gas to sodium hypochlorite. As for amount of chlorine it is sufficient to maintain 10 mg/l residual. Commented Sep 17, 2022 at 20:35

Add calcium hypochlorite and a non-metal algicide.run pool pump overnight

  • 3
    How much calcium hypochlorite?
    – Niall C.
    Commented Feb 12, 2016 at 14:41

Switch to non chlorine shock and you wont get the same reaction

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