Phosphates & Nitrates in Swimming Pools


Phosphates are pollutants....

Phosphate became a household word in the 1970's. This is when people started to use low-phosphate and phosphate-free laundry detergents. This was to protect lakes, streams, wetlands and other runoff areas from the detrimental effects of excess phosphate. One of these effects is unwanted algae blooms. It created such a fervor - remember the movie Swamp Thing?


Phosphates Accumulate in Pools....

What's true for lakes is also true for swimming pools. Phosphate is a natural component of most swimmer wastes. It is also present in rain water. Phosphate is persistent and does not break down naturally. Landscaper's fertilizers, which may blow into the pool, have high phosphate content. For all of these reasons, pools can quickly build up high phosphate levels. This creates an abundant and tasty food source for all strains of algae, and can make controlling their growth difficult. Remove the food, and you have a strong weapon against algae.


When Phosphates are Present, Algae Grows....

Phosphate is the main ingredient in fertilizer. Phosphate is plant food, and algae are plants. If you have had persistant trouble with algae, every year - and it always seems to come back, you may have a phosphate problem in your pool. When excess phosphate is present in a swimming pool, the symptoms often include the following:

  • Cloudy, Green Water

  • Slippery and Slimy Surfaces

  • Mustard and Green Colored Debris

  • Excessive Chemical Consumption

  • Poor Water Quality

Remove the Phosphates and Solve the Problem....

The maximum level of phosphate in pool water should be 0.1 ppm. Once the phosphate climbs above this level, the water quality begins to decrease and slime deposits can begin. Fortunately, draining to eliminate the accumulated phosphate is no longer necessary. Natural Chemistry's Phos-Free is a natural mineral compound which effectively and rapidly reduces the level of phosphate in the water. Phos-Free is a natural mineral product which is non-toxic. It is safe to store and use around children. Great Lakes Bio also produces a phosphate remover under the name of Orb-3 Phosphate remover.


After great success with Phos-Free phosphate remover, Natural Chemistry has added Phos-Free to to their Pool Perfect Concentrate. You can test for phosphates in your pool with the AquaChek Phosphate Test Kit

Nitrates are no fun in the pool!
Nitrates are a matter similar to Phosphates, but of different origin. Their big similarity is that they are both a food source for algae. Nitrate is a plant nutrient and is present in all green plants and fertilizers. It is natural occuring and is found everywhere something is growing.

Nitrites (NO2) are a close cousin to Nitrates (NO3) and are just as much of a problem for pools, because when a Nitrite comes in contact with water, it easily gains another Oxygen atom to become a Nitrate. This additional atom gives Nitrates real stability, and makes eradication difficult. In fact, the only known way of Nitrate removal in pools practiced today is to drain a portion of the pool, and refill with water that is Nitrate free, if possible. Shocking a pool heavily will revert the Nitrates back to Nitrites, but from their once again, an additional Oxygen atom is easy to come by in a swimming pool filled with H2O.

Where do Nitrates come from?
Rural areas - those with water wells and septic tanks are particularly prone to Nitrate contamination in pools. Fertilizer is the most common source of Nitrates in pools. Do birds and ducks make regular passes over your pool? Do they land in the pool to bathe? Birds and especially Ducks can do a real number on a pool. Rain spilling off of overhanging trees can add Nitrates to a pool, and even acid rain itself, so common in the Northeast, can increase Nitrate levels. Finally, human waste, sweat, cosmetics can all bring traces of Nitrates into the pool.

According to John Girvan, one of the few people to study Nitrates extensively, has said that "With nitrate in the pool," he says, "you will get algae and other contaminants that won't respond to normal treatment." Some pool techs have been known to say that Nitrates "lock up chlorine". The opposite is in fact true, the presence of Nitrate in pool water will drastically increase the sanitizer consumption.

At levels as low as 10ppm of Nitrate, algae will grow even though you have used algaecide and are keeping a proper chlorine residual. But keeping a proper residual of chlorine in the water can prove to be difficult when Nitrates are present. This is what tricks people into believing in Chlorine Lock, it's not blocking chlorine, but using it very quickly.

What can be done to Eliminate Nitrates in my pool?
There still however is no chemical to remove the Nitrates from the pool water, so if you have a contamination, you will need to drain most if not all of the pool water. Locating the source would be advised, to prevent re-contamination of the pool. Animals, water run-off, wind blown fertilizers, well water are all likely sources. Check your bathers! Sweat, oils, cosmetics and hair treatments may contain Nitrates. Dogs and Ducks bring all sorts of nastiness into the pool, and should be discouraged. If you have a Duck Problem in the pool, keep ducks out of your pool using Duck Off, made by Lo-Chlor.