The White Bucket Test: How to Identify Green Pool Water

Identify the Cause of Green Pool Water

Using the White Bucket Test


Why is my pool green? Well, that depends. There are many factors that can lead to a green pool, and this procedure is a quick, simple, and reliable way to know for sure. Green pools usually occur for one of these three reasons:

  1. Algae or other organics (tannins)
  2. Copper oxidation
  3. Too much total alkalinity relative to calcium hardness
  4. Bonus: Bromine pools

Simply pouring chlorine into the green pool might be your first instinct, but if the problem is too much copper in the pool, the chlorine will only make it worse. Conversely, if you assume it's copper and put in SC-1000, but the problem was actually algae, now your chlorine will be reduced by SC-1000 that has not yet bound to calcium or metals. Trust us, we have made both mistakes more than we want to admit. 

Using the white bucket test, you don't have to guess or assume why your pool is green.

Related Procedure: The Orenda Green Pool Cleanup

You will need:

  • clean white bucket
  • A stirring stick 
  • Camera or smartphone
  • Liquid chlorine

The White Bucket Test

This test involves chlorinating a bucket of green pool water and observing the change in color.

  1. Use a clean white bucket to scoop a sample of green pool water (nearly full bucket).
  2. Observe the green tint to the water and take a photo with a camera or smartphone camera.
  3. Add one ounce (1 fl.oz.) of liquid chlorine to the bucket, then stir.
  4. Within 30 seconds you should notice a difference in color.
    • If the water clears up, your pool is green from algae (or tannins), but
    • If the water gets greener or darker, your pool is green from copper.
    • If there is no change in color, test your total alkalinity and calcium hardness levels.

Chlorine added to the bucket gives you an immediate picture of what would happen if you poured chlorine into the pool...but in a separate sample. The white bucket allows us to see the green tint of the water for color contrast. Chlorine either kills the algae (and clears the water) or it oxidizes copper (and darkens the water). If no color change is observed, test your total alkalinity and calcium hardness levels. If your TA is too close (or higher) than your CH, water can turn green. Strive for a 3:1 ratio of calcium hardness to total alkalinity to avoid this.

Once you know why your pool is green, then you can address the problem accordingly.

Related Procedure: How to Implement the Orenda Program

Frequently Asked Questions (FAQ)

What if the pool is green but chlorine is high?

If your pool is green and chlorine is high, that usually means copper oxidation. It is also possible with algae and improper TA/CH ratios, but it's rare.  Still do the white bucket test to find out.  Oftentimes high chlorine does not necessarily mean fast killing rates. For instance, if your CYA is too high, you could have high chlorine but it is slowed down. You may also have other contaminants in that water like nitrogen compounds, which also tie up chlorine.

Are there other sources of green pool water?

Apart from using dyes to deliberately color water green, we are unaware of other causes at this time. But we are always learning, so if you know of another reason, please let us know!  One other possibility is that certain pool surface colors can distort light so that water looks green. We saw a plaster surface one afternoon that made the pool look emerald green, only to find out the homeowner specifically asked for that color.  Again, the white bucket test would quickly show you the water was not actually green.

We should also mention bromine. Bromine tends to turn water into a slightly greenish-blue color. It's not enough to show green in a white bucket test, however.

More Questions?


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