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Phosphates are something that many pool owners aren’t aware of yet have a dramatic effect on the overall condition and appearance of their pool.  Phosphates are an inorganic chemical that can impact the pool chemistry in a variety of ways.  You can have a firm understanding of all of the basic pool chemistry components (chlorine, pH, total alkalinity, calcium hardness, etc) and still have difficulty maintaining a clear, balanced pool if you don’t know about phosphates.  These issues often seem to come from nowhere and are mystifying if you don’t know that they are resulting from phosphates.  So, let’s dive in and learn about this pesky little compound!

Some facts about phosphates:

  • Phosphates are present at some level in many (if not most) swimming pools

  • Pools can have clear water and operate normally with low levels of phosphates

  • Phosphates can exist “invisibly” in water, unknown until a problem occurs

  • Even minor fluctuations in normal water chemistry, changing weather, or increased usage of the pool can cause dramatic water problems if phosphates are present

  • Pool water chemistry is almost impossible to maintain if high levels of phosphates are present

  • Most pool chemicals are measured on a parts per million scale (ppm).  Phosphates are measure on a parts per BILLION scale (ppm).  This means that 1/1,000th as much phosphate can effect the pool as much as other things do!  In other words, a VERY VERY small amount of phosphates can have a HUGE impact on the pool!

Where phosphates come from:

  • Animal droppings (both wild and domestic).  Birds, dogs, and raccoon droppings on a pool deck are often sources of phosphates in the pool.

  • Lawn and garden fertilizers.  As time has gone by fertilizers are the biggest source of phosphates in a pool.  These days many people have landscaping or lawn in close proximity to the pool.  Gone are the days when pools have massive concrete decks stretching in all directions, buffering the pool from the effects of lawn and garden areas.  Additionally the prevalence of more potent fertilizers and spray-based fertilizer programs has caused a huge increase in pool phosphate problems.  Even if you don’t have a landscaping company that uses spray fertilizer, if your neighbors do it is very easy for the spray to travel a distance on a windy day and end up in your pool.  As mentioned, it takes a VERY small amount of phosphate to impact the pool.

  • Fill water.  Some municiple water has phosphates in it, but well water is especially prone to Phosphate problems.  At Atlantis Pool Service we have documented extremely high phosphate levels in well water in Barrington and Jamestown in particular.  If your well is located in an area where many homeowners fertilize their lawn then it is drawing water from water tables high in phosphates.

  • Makeup, lotions, sun block.  Many lotions and cosmetics have phosphates in them.

  • Certain pool chemicals.  Specifically metal remover has phosphates in it.

Problems Caused by Phosphates

The most common problem caused by phosphates is algae.  Phosphates are used to fertilize your lawn and in the same way they also fertilize algae in your pool.  Phosphates are food for algae.  Sudden algae blooms that appear out of nowhere in a pool that is properly chemically balanced are almost always the result of phosphates.  Persistent algae problems that aren’t resolved by algaecide or shocking again almost always are caused by an underlying phosphate problem.  

Phosphates can also cloudy issues with cloudy water.  High levels of phosphates can sap the effectiveness of chlorine causing murky or cloudy water.  If your chlorine levels are balanced yet the water isn’t clear, phosphates can be the issue.

Unusual staining that isn’t caused by organic matter, metals, or algae can be due to phosphates as well.

The descriptions and wording contained on this webpage are exclusively the property of Bryan Mills / Atlantis Pool Service LLC.  Any reproduction or use without the consent of Atlantis Pool Service is strictly prohibited.

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