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Purple Cyanurate is most often seen in the spring at pool opening. Although it has been "noticed", cooler water (under 68 degrees Fahrenheit) helps this reaction more readily occur.


Purple or Copper Cyanurate is further made worse by the following water balance issues:

1. High pH - over 7.8

2. High Total Alkalinity (TA) - over 150 ppm


3. High Cyanuric Acid (stabilizer, conditioner) level over 100 ppm.

For this reason alone it is NEVER a good idea to add CYA or stabilizer unless the water has been properly tested & analyzed. CYA should NEVER be added unless the level is BELOW 30 ppm. At spring opening it is always a good idea to allow the water to circulate for at least 48 hours continuously with the return jets or fittings pointing to the bottom of the pool to create better overall circulation. Also keep in mind that when testing pool water, high CYA levels can & will produce an INACCURATE Total Alkalinity level. Proper testing, analysis & balancing is required to correctly adjust the TA and pH.


4. Copper present in the water - especially if over 0.5 ppm. Copper can come from a variety of sources: home piping, pool heater, certain algaecides & ionizing systems, etc.


When all of these factors come together, you will experience the staining that you see in the pictures. THIS IS NOT PINK SLIME!










Prevention: Prevention of "Purple or Copper Cyanurate" is preferred over treatment. Follow these steps to prevent Purple Cyanurate:
1. Maintain proper water balance: pH 7.4 - 7.6, TA 80 - 140 ppm, Calcium hardness 175 - 250 ppm.

2. Only add stabilizer in Chlorine treated pools AND only when the CYA level drops below 20 - 30 ppm. If you are using a slow-dissolving type of chlorine tablet or stick, those products will naturally release CYA into the pool over the course of the summer. Only use copper based algaecides when treating severe algae problems.

3. Properly maintain & adjust the pH & TA 4. Adding an initial dose of Naturally Free has provided excellent & quicker treatment of the purple staining.

4. Be patient! The Purple will eventually (sometimes as long as 2 to 4 weeks) to be re-absorbed into the water especially as the water warms. Sorry, but there is NO quick fix.

5. If you have recently switched from a slow dissolving chlorine system (tabs or sticks) where the CYA will most likely be high (over 100 ppm) to a copper based treatment system such as Pristine Blue or other product, you would be wise to lower the CYA to 40 ppm or under before winterizing to help prevent the potential problem of Copper Cyanurate.

Treatment: Treatment of "Purple or Copper Cyanurate"
1. Reduce the CYA level to under 30 ppm by partially draining & refilling the pool with fresh water. After a partial drain & refill, allow the water to filter & circulate for 48 hours before testing.

2. Reduce the amount of copper present in the water (especially if over 1.0 ppm).

3. Properly adjust the pH & TA as noted above.

4. Adding an initial dose of Naturally Free (a formulation of natural metal chelating agents) has provided excellent as well as quicker or faster treatment of the purple staining.

4. Be patient! The Purple staining (the copper) will eventually (sometimes as long as 2 to 4 weeks) be re-absorbed into the water.

There is NO quick fix to the Purple Cyanurate staining. It has to work its way out on its own.

"purple or copper cyanurate"  -  purple stains vs. pink slime

Purple or Copper Cyanurate is caused when the Cyanuric Acid (chlorine stabilizer or conditioner) is allowed to become "high" or usually over 100 ppm and it then reacts with any copper that may present in the water.


Purple Cyanurate is a chemical/mineral imbalance problem. It is NOT an "organism" or algae problem.


Furthermore, it can appear that the staining is similar to "crystals". See the pictures below sent in from one of our customers.Purple Cyanurate "stains" cannot be easily scrubbed, scraped or removed. It must be chemically treated.

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Purple Staining