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Ammonia and Nitrates in Swimming Pools

By Terry Arko

The Real Problem

Ammonia as we know it does not exist in pool water due to the quick reactions that take place. Products that contain ammonia are not the problem in pools. The real problem is from organic nitrogen when it combines with chlorine to form organic chloramines. As mentioned previously organic chloramines are much more difficult to remove from water and they are a source of toxic air and overwhelming chlorine odor. The main source of stubborn organic chlorine is from organic debris and excessive swimmer waste and not from using ammonia-based products.

The Nitrogen Cycle

Nitrogen makes up 78 percent of our atmosphere. Easily assimilated through our breathing, oxygen makes up 22 percent of the atmosphere. If it were not for oxygen, fire would not burn and we would all suffocate. Therefore, we can all be grateful.

While nitrogen is more abundant, it also is more difficult to distribute into the environment. Humans and animals need nitrogen for the synthesis of proteins and in the form of nitric acid for proper blood flow. Nitrates are a primary ingredient in fertilizers for food production. They are also key to the production of gunpowder. Near the beginning of WWI, the world was on the brink of food shortages and there was a shortage of gunpowder. A German scientist named Fritz Haber discovered a method for creating ammonia by synthesizing it from atmospheric nitrogen. His process of nitrification of ammonia proved successful and there was enough nitrate derived to grow the world's food and to fight its battles. Fixation is the process that releases nitrogen from the atmosphere by lightning strikes or bacteria in soil. The nitrifying process starts when nitrogen in air pockets of the soil fix to bacteria. Further reaction of bacteria with nitrogen leads to ammonia. Ammonia is broken down further into nitrite and then finally as nitrates. In soil and certain plants denitrifying bacteria converts nitrates back into nitrogen. The released nitrogen goes back into the atmosphere. This is the nitrogen cycle.

Nitrogen ends up in swimming pools from storms, via human or animal waste and algae growth. Poor disinfection, algae or lots of organic debris will increase nitrates. Replication of the nitrogen cycle takes place in poorly maintained pools by certain nitrifying bacteria like pseudomonas. Pollen can distribute nitrogen into pools. Excessive blue-green algae in pools contains cyano-bacteria which is nitrogen fixing. Green pools take more nitrogen from the atmosphere and nitrification leads to more nitrates. In farm areas, nitrates are present in the groundwater.

There are tests available for nitrates. Test for nitrates before filling a pool with well water. The recommended maximum level for nitrates in drinking water is 10 ppm. This applies to swimming pools although some state that 10 to 25 ppm is allowable. High levels of nitrates do not pose a health threat to adults. However, in infants to toddler age consumption of nitrates can lead to hemoglobin or "blue baby syndrome," a condition that causes a lack of sufficient oxygen to the red blood cells.

Understanding the Effects of Nitrates

The most abundant form of nitrogen in pools is not from ammonia but rather from nitrates. Ninety percent of ammonia in pools oxidizes to nitrogen then releases back into the atmosphere. Heavy swimmer loads with excessive waste, large amounts of organic debris and algae in pools are the primary culprits to high nitrate levels. In short, a well-maintained pool free of organic debris with routinely performed practical oxidation will not experience problems from nitrates. While storms bring in nitrates, immediate shocking afterward can keep them at bay. Dealing with algae quickly also helps reduce the mechanism for the formation of nitrates. Nitrates at levels above 25 ppm can lead to rapid decomposition of free chlorine and excessive algae problems.

Removing Nitrates from Pool Water

The most practical and cost-effective way to reduce nitrate levels is by draining and dilution. Diligence in maintenance and proactive oxidation help prevent the causes of nitrates. Installation of secondary oxidation units like ozone and UV may be effective at prevention. Apply immediate oxidation after heavy swimmer loads, storms, application of fertilizers in proximity of the pool or any unusual contamination event. Remove or treat excessive organic debris from leaves, grass or pollen. An enzyme can help to break pollen down quickly. Clarifiers can help in faster removal of nitrogen containing particulate to the filters. Regular backwashing and cleaning of filters helps by keeping bacteria and nitrogenous materials from forming inside the tank.


  • Ammonia as we know it does not exist in pool water because it reacts with hydrogen ions to from ammonium ions.
  • Ammonium ions oxidize rapidly by proper free available chlorine.
  • Ammonia-based specialty chemicals will not cause poor water quality.
  • Organic nitrogen compounds (organic chloramines) are the real problem in pools because they oxidize at a much slower rate than ammonia bound chloramines (inorganic chloramines).
  • Ammonia contributes less than 10 percent of nitrates in pools.
  • Poorly maintained pools with persistent organic debris and algae will cause increased nitrates. Wild animals, ducks and birds can bring nitrates in through waste.
  • Nitrates can increase in pools immediately after a storm.
  • Urine and perspiration in reaction with insufficient free available chlorine are primarily responsible for toxic chloramines and increased nitrates.
  • Proactive oxidation and proper maintenance can help to prevent the increase of nitrates.
  • Test groundwater in agricultural areas for nitrates before filling pools.

Terry Arko has more than 30 years of experience in the pool and spa/hot tub industry, working in service, repair, retail sales, chemical manufacturing, customer service, sales and product development. A certified pool operator (CPO) and CPO instructor through the National Swimming Pool Foundation (NSPF), Arko is currently a water specialist for NC Brands, parent company of SeaKlear and Natural Chemistry, which is a manufacturer of pool and spa products. For more information, visit www.ncbrands.com.