Phosphates and Pools

During the current decade, phosphate removers for algae control in swimming pools have become widely used and also misused. Phosphates (also denoted as PO4) are known nutrients to help increase plant growth rates such as in algae. However, there are several debates (and confusion) regarding phosphates in pool water.

The first debate focuses on the acceptable level of phosphates in pool water to minimize algae growth. Several vendors of phosphate remover products state that the maximum level should be 125 p.p.b. (parts per billion) or .125 p.p.m. (parts per million). Others state that phosphates are not a concern until they exceed 1000 p.p.b. or even higher.

The second debate centers on how phosphates actually enter into pool water. Some say they enter from the source water, fertilizers, wind blow dirt/dust, plant debris, or even rain water. Other’s state that cities treat their municipal water sources with phosphates, and finally, others claim that phosphate based scale and stain products are the primary source of phosphates. Who’s right in these debates?

Sixty percent of pool owners experience two (2) full algae blooms every season. Algae blooms place a high demand on the chemicals present in your pool water and cost time and money in clean up.

While everyone agrees on how to kill algae once it’s taken over your pool. Regardless of how this happens, if phosphates are allowed to remain present in pool, spa or pond water, they will be reduced to orthophosphates, which are the only form of phosphates that algae can digest. Orthophosphate levels should remain below the 250 p.p.b. (parts per billion). Once levels exceed the 250 p.p.b., algae becomes increasingly resistant to sanitizers, including chlorine shock.

 But what happens if your pool is equipped with a Salt Generator / Chlorinator

Salt generators have gained in popularity recently, but the technology goes back to 1800 when scientists discovered the technology of splitting molecules in a solution using what is called electrolysis.

Salts like sodium chloride or sodium bromide are used in a solution that is subject to low-voltage electrical current and a pair of cells with opposing charges. One cell, the anode contains positive charges, and the cathode contains negative charges. Electrical ions flow back and forth between the two cells. When sodium chloride passes across these cells, molecules are split and chlorine gas is produced at the anode. Hydrogen gas is produced at the cathode. Salt generators produce hydrogen gas, chlorine gas and a solution of sodium hydroxide. When salt generators are working properly, they are continuously producing free available chlorine to proper set percentage levels.

When levels of phosphate exceed 250 p.p.b., the unit can cease to produce enough free available chlorine to keep up with demand. Most manufacturers of salt chlorine generators will confirm that when there is a problem with production of free available chlorine a phosphate test is recommended. If the phosphate levels are near or over 250 p.p.b., a phosphate removal treatment is advised. 

• What Happens When Salt Generators Fail?

When a unit begins to fail, it will not produce sufficient free chlorine to keep up with demand. There are numerous reasons for failure, including dirty or calcified cells that need to be cleaned, no power to cells, or insufficient levels of salt in the water. 

But, there is one main factor to consider first when a salt chlorine generator fails, the presence of phosphates in the pool water.

• Phosphate problems with well water?

Most likely the well water contains iron, as well. You would need to use some sort of filtration to handle most of the iron, copper and other heavy metals, from the water.

However these will not remove phosphates. 

You will need to use a phosphate remover that will precipitate the phosphates, so they can be vacuumed and/or filtered out.

Removing the Phosphates

It is important to understand that orthophosphate in pool water exists in a soluble form. The most effective phosphate removers work by making the soluble orthophosphate precipitate out as a solid. This will cause some cloudiness in the water, which can be filtered out readily with the use of a clarifier. However, keep in mind that the more phosphate, the more cloudiness there will be. In extreme cases it can take up to three days for the cloudiness to clear completely. It is important during this cloudy period to have the salt chlorine generator turned off until the water clears. During this period liquid chlorine can be used to keep the residual up. The other option for extreme levels of phosphate when levels are near or over 5,000 p.p.b. would be to drain and dilute some or all of the water. The drain and dilution method may be better used for commercial pools where shut-down time is limited and cloudiness of the water is regulated. In these cases it is advisable to dilute out as much phosphate as possible and then use maintenance doses of phosphate remover to keep levels managed.

Who invited phosphates to the party, anyway?

The challenge with phosphates is that they are constantly being introduced into your swimming pool water. They are found in lawn and garden fertilizers, decaying vegetation, municipal water, cosmetic items on bathers, and even other pool chemicals. This means a fresh batch of phosphates enter your water when any of the following occur:

• The wind blows dirt into your pool and/or spa.

• Sprinkler run off from your lawn or landscaping enters your pool and/or spa

• Your water lever puts fresh water into your pool.

• Leaves, twigs or bark enter your pool and/or spa water

• Any chemical containing TSP or any amount of phosphoric or other phosphorous based ingredients to clean your pool and/or spa.

As such you can never completely remove phosphates, instead, we refer to it as maintaining a “near zero” level with a long-term solution that includes a blend of using phosfree products, regular water testing, correct sanitizer levels, and limiting exposure to phosphates.

Let Clearwater Pools show you how our proactive approach to preventing anything from blooming in your backyard, but your prized begonias, in lieu of reactive with huge amounts of chlorine shock and a scrub brush – will stop algae blooms and make your sparkling pool water the crown jewel of the neighborhood.