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Green And Cloudy Water In A Pool

Items needed to determine and fix the cause of green and cloudy water in a pool:

The most common culprit for green and cloudy water is algae.  However, there are a variety of reasons for it.  These instructions are given in order of likelihood and priority.  The first steps have to be solved before the next ones can be.

Things that will cause algae are:


  • Phosphates
  • Filter Needs Cleaning
  • Water Imbalance
  • Poor Water Circulation 

How To Fix Water Balance and Phosphates

1)  Test pH.  Knock the pH down to the low side of the 6.6 - 7.0  range (6.6)

2)  Test Copper.  Bring the copper up to .4 ppm - .7 ppm.  If the copper does not rise above .3 ppm, test the calcium.  Bring the calcium up to 400+ ppm (minimum 300 ppm).  

3)  Test Phosphates.  Make sure they are under 200 ppm.  If there are any phosphates in the water use a recommended phosphate remover.

4)  Use 1 quart non-metal algaecide during daylight hours - best in the morning.

5)  Wait 12 hours and use 5 lbs per 20,000 gallons of pool water non-chlorine shock  (peroxymonopersulfate).

6)  Wait 24 hours and if the pool is less than 90% clear, add another 5 lbs per 20,000 gallons of pool water non-chlorine shock.

Filter Cleaning

Sand Filter With Sand or Glass:

1)  Take the top off of the filter and examine it.  Take out debris and check for dips in the media that might indicate a broken lateral.

       a)  If the filter is a sand filter with sand, pour a couple gallons of liquid acid in the filter covering the media.

       b)  If the filter is a sand filter with GlassPack Filter Media, pour in 2 gallons of regular household bleach, covering the media.

2)  Let the filter sit overnight and then backwash to waste.

DE Filter:   

1)  The filter should be broken down, the grids removed and soaked in a 2 parts water to 1 part liquid acid solution for 12 hours.  

2)  Reassemble the grids 

3) Add DE powder.

Testing Circulation

While the pump and filter are running, place a beach ball (or something that floats) on the surface of the water and watch how it moves.  If it gets stalled someplace that means the pool water isn't circulating effectively.

Make sure all return jets are pointing straight to the middle of the pool, not up, down or sideways.

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