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Recognizing & Treating Metal Stains

That black algae that no matter how often you brush and shock it, it won’t come up.  The odd rusting of your fiberglass steps, that couldn’t possibly be rusting as they’re not made out of metal.  The weird yellowing of your return jets and skimmer faceplates.  A purple “I don’t know what” at your water line.  What is this stuff?  WHY is this stuff? What do I do?

These are more than likely stains resulting in a metal deposit.  In ground pools tend to be susceptible to these nuances (especially fiberglass pools) than an above ground pool.  These stains have many sources and can occur at any time if the conditions are right.  It is key to understand how to determine what the stain is, how the stain is treated and what you need to do to prepare your water for the best possible outcome once you begin treatments.

Algae or Metal?

Many people see discoloration of their in ground pool surface and automatically begin to treat it as if it was an algae outbreak.  In most cases, the stains I described above are metal deposits derived from copper and/or iron.  But how can you be for sure?

To identify if the stain is a metal, you may take citric acid and apply it directly to the stain.  Citric acid- A wedge of lemon/lime/orange, vitamin C tablet, etc- will chemically lift any copper or iron stains you may have.  The majority of these deposits will lift immediately but it may be an hour or even overnight before you see a difference.

To identify if the stain is a suborn algae,  you may try taking a chlorine tablet, wrap it in a rag, and rub it gently on the surface that is stained.  However, this is not the preferred practice as it can be detrimental to vinyl, and we prefer to have our customers handle the chlorine tablets as little as possible.

The Terrible Triumvirate.

Its a Metal.  What do I do?

Conventional wisdom is to dive right in with metal removers and sequestering agents.  However, it is preferred to make sure that you water is balanced and your chlorine level is 1.5ppm or less.  Having these ideal chemistry levels will go a long way in removing stains and keeping them from redepositing on your pool surface.  Metal removing products can be costly so lets not waste money.

Once your pH and alkalinity are in balance and your chlorine level is lowered its time to attack the stain head on.  Add Abscorb-X to the affected areas.  The stains should be chemically lifted within minutes of the application.  Following up with Stain & Scale Control is recommended, as while Abscorb-X will remove the stain, it will not remove the cause of the stain (again, copper and iron).  As a sequestering agent, Stain & Scale Control should be applied to physically remove the offending metals into your filter system so they can be removed the next time your filter system is cleaned.

For a more complete step-by-step analysis of the stain removing process, click here.


The Metal is Gone.  How do I Keep it Out?

Using a sequestering agent such as Stain & Scale Control or Stain-X on a weekly basis is highly recommended to keep deposits from re-forming.  For best results be sure to use either of these products with a balanced pH and alkalinity and with a chlorine level of >2.0ppm.  Additionally, you should not shock your pool 3 days prior or 3 days after a metal treatment.  Be sure to regularly clean your filter to rid the system of sequestered metals.


Still Not Getting It?

Always feel free to bring your water to a professional to have in analyzed to make sure you’re pool waters’ chemistry is in the best position to succeed.  Feel free to email us or contact us in the showroom with any water chemistry questions.

Stay cool with an stain-free pool and good luck moving forward,

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