Phosphates in pool water

Phosphates in pool water

Phosphates can be a concern in swimming pool water as they can contribute to various water quality issues. Here’s what you need to know about phosphates in swimming pool water.

Sources of Phosphates: 

  • Rainwater and runoff containing organic matter
  • Yard debris, such as leaves and grass clippings
  • Swimmer waste (e.g., urine and sweat)
  • Fertilizers and lawn treatments
  • Some pool chemicals and algaecides
  • Bird droppings and other organic contaminants

Effects of Phosphates

Elevated phosphate levels in pool water can lead to several problems.  These include:

  • Algae Growth: Phosphates can serve as a nutrient source for algae. High phosphate levels can promote algae growth, turning your pool water green.
  • Reduced Sanitizer Efficiency: Excessive phosphates can hinder the effectiveness of pool sanitizers (e.g., chlorine), leading to inadequate disinfection.
  • Cloudy Water: Phosphates can contribute to cloudy or hazy pool water.

phosphate remover

How to remove phosphates

If your pool has high phosphate levels, you can consider various methods to reduce them:

Phosphate Removers: These products are available in liquid or granular form and can effectively reduce phosphate levels. They work by binding with the phosphates and causing them to precipitate, making them easier to filter out.

Proper Filtration. Regularly cleaning and maintaining your pool filter is essential to remove suspended particles, including phosphate compounds.

Reducing Contaminants. Minimize the introduction of phosphate sources into your pool by keeping the pool area clean and free of debris, using a pool cover, and avoiding the use of phosphate-containing pool chemicals.

How to prevent phosphate buildup.

  • Regularly skim and vacuum your pool to remove organic debris.
  • Maintain proper water chemistry, including chlorine levels, to prevent algae growth.
  • Follow a pool maintenance schedule and use appropriate pool chemicals.
  • Use a pool cover when the pool is not in use to reduce debris and runoff.

How to test for phosphates

Phosphates in pool water are measured on a different scale than all other elements. Importantly, phosphates are measured in parts per billion (PBB), not part per million (PPM). Remember, that this is because if they were measured in PPM then the numbers would always appear to be very low. For example, 5PPM of chlorine can also be correctly expressed as 5,000PPB. Notice how dramatic 5,000 PPM sounds compared to 5 PPM.

Under normal circumstances, phosphates are not usually a big issue for most pool owners.  A low level of phosphate is usually not a problem so don’t think you need to add expensive products constantly to keep the number at zero.  However, removing high levels of phosphates is a good idea and will be a big help to water clarity.  

My pool keeps turning green

If your pool water seems to always be on the verge of going green or cloudy, then high phosphates in pool water are often the cause. Also, if the free chlorine is not high enough this can make clear water harder to achieve. We have a page about this that provides further information about this.

If your water is turning green and there are no phosphates then it could be time to shock chlorinate the pool water.  This will kill off the chloramines and allow your chlorine to be more effective in killing algae.  It is a good idea to shock chlorinate your pool every 6 months.

In summary, it is important to remember that there are many aspects of water chemistry. Therefore, maintaining a broader perspective is important. Sadly, not all pool shop staff are trained to see beyond what the computer tells them to sell. Therefore, this means some poor folks end up on an endless product merry-go-round that never seems to solve the problem.


Final thoughts…

Maintaining proper water quality in a swimming pool involves monitoring various parameters, including chlorine levels, pH, alkalinity, calcium hardness, and more. Phosphate levels are just one of these parameters, but they can be particularly important in preventing algae growth and maintaining overall water quality.

Some pool shops may not routinely test for phosphates unless specifically requested. It’s a good practice to ask for phosphate testing when you have your water tested, especially if you suspect issues with algae or water clarity. Regular testing and maintenance, along with proper filtration and chemical balance, are essential to keep your pool water clear, safe, and enjoyable for swimming.