Guest Column - October 2010
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Pool / Aquatics

Failing Salt Generators
The Phosphate Connection

By Terry Arko

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 ppb 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.

Keeping Them Out

It is important in a salt chlorine pool to be diligent about keeping phosphate levels down. The following are some guidelines that can help:

  1. Test water for phosphates on a weekly basis.
  2. Treat with a phosphate remover weekly to keep levels down.
  3. Use only non-phosphate metal products and cleaners.
  4. Clean and remove grass, leaves and any organic debris from the pool as quickly as possible.
  5. Test tap water to see what levels of phosphate are in the source.
  6. Test for and treat for phosphates after any periods of extreme weather or heavy swimming.

For commercial pools avoid using any phosphate-based cleaners for the decking or tile. Many seasonal outdoor pools are near lakes. Operators should discourage patrons from visiting the pool after swimming in lakes. Thorough rinsing in showers should be done. Source water should be tested for phosphates as well. Many water municipalities treat with straight orthophosphates at different times. If this is the case then phosphate treatment is recommended at filling and whenever topping off.

The method for winterizing a salt generator pool is not that different from a regular pool. In areas where winter is extreme and a hard shut-down is used, the pool should be drained down and winterizing chemicals added as usual. The salt generator should be inactivated and in some cases disassembled and stored for the winter. Check with the generator manufacturer for specific winterizing instructions. In some areas a complete shut-down may not be necessary. In these areas you would simply turn down the hours of filtration operation and reset the generator to run in accordance. In winter water temperatures there should be sufficient chlorine produced from the unit in two hours a day.

Knowing the underlying water chemistry in pools is a key component to making sure that salt generators work properly. In a salt chlorine pool, keeping the phosphates low is the secret to letting the free chlorine flow!


Terry Arko has more than 30 years of experience in the swimming pool and spa industry. He has worked in service, repair, retail sales and chemical manufacturing. With expertise in swimming pool water chemistry, he is both a Certified Pool Operator (CPO) and CPO Instructor through the National Swimming Pool Foundation (NSPF). He is currently product specialist and Northwest Territory sales representative for SeaKlear Pool and Spa Products. For more information, visit