What Causes The Purple In My Pool?

What Causes The Purple In My Pool?

If you notice hints of dark, deep purple hues lining the walls of your swimming pool, your pool may have a mineral problem. If you’re worried about the staining becoming permanent, don’t worry, as the solution is a relatively quick fix.

This article will go more in depth to help you remedy your purple pool back to a clear and refreshing swimming spot.

The Minerals For Purple Haze

Pools can hold various minerals that can affect the composition of the water. There are two types of minerals that primarily cause pools to turn purple - manganese and copper cyanurate. Both are purple mineral stains, but the colors may vary depending on the concentration of the minerals that interact with the chlorine in your swimming pool. The chlorine added to the swimming pool can oxidize with the metals and cause a noticeable reaction in your pool.


Manganese Treatment For Pools

Manganese can cause stains on pool plaster and tile grouting. Corrosion of stainless steel and low calcium levels can keep it in a state of suspension, but if left untreated it can stain most of the pool surface.

Here are some recommended steps to correct purple pool coloring from manganese*:

  1. Place half a pound of pH reducer powder in a small white sock and drop it in the colored area for 30 minutes. If there is a big change in color, then the problem is manganese.
  2. Raise the water level of your pool until it is above all the stains.
  3. Add muriatic acid. Gauge the amount based on the desired pH level and pool size.  Watch the pH level until it drops to 6.8, as you cannot remove the stains without lowering the pH level.
  4. Brush stains away once a day for two consecutive days.
  5. To remove the manganese debris and help prevent the stain from returning quickly, clean the filter regularly.
  6. Get the calcium back to 200ppm and add two to three doses of mineral treatment (chelating agent) once all the stains have disappeared. Higher dosages should be used if there are other minerals present, but not necessarily detected.
  7. Add soda ash to raise the pH from 7.4 to 7.6 (using chart based on pool size and desired pH level to determine the amount)
  8. If there are trace amounts of manganese present, practice stain avoidance treatment to get ahead of the issue.

Copper Cyanurate Treatment For Pools

When water contains high levels of cyanuric acid (roughly 100ppm+) and non-chelated copper, the composition results in copper cyanurate, which can form purple crystals along the waterline, walls and pool bottom.

Copper cyanurate can be caused by the galvanic corrosion of materials in salt pools. One method to prevent this coloration from occurring in salt pools is installing a sacrificial anode.

The anode is made of zinc, which doesn’t stain and holds more voltage than other metals, so galvanic corrosion strikes it first, instead of ladders and other metallic components from contributing to copper wear.

Here are some recommended steps to correct purple pool coloring from manganese*:

  1. Lower the water CYA level to roughly 40 and 50 ppm by performing a partial drain and refill.
  2. With the CYA adjusted, trap the copper using a metal control product.
  3. Get the pH and total alkalinity back to normal levels, and the stains should disappear over time
  4. Place preventative measures to ensure copper cyanurate never forms again. Keep an eye out on CYA levels and avoid overusing stabilizers and copper-based algaecides.

Whether you have high levels of manganese or copper cyanurate clouding your pool with purple haze, at the end of the day, proper pool maintenance can effectively prevent your pool from producing a purple color. If you want to ensure both you and your pool stay healthy and mindful, keep your tub balanced with pHin. It constantly monitors your water and tells your smartphone what you need to do to keep the water in your pool healthy. Use it with your own chemicals for flexibility or get our single-dose, pre-measured chemicals delivered to your door. If you need someone to service your equipment, Pool Service on Demand connects you to local, qualified pool techs.


*Consult with your pool manufacturer or local pool store before taking these steps.

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