Phosphates are algae food, and they are impossible to avoid. Phosphates are introduced to your pool is serveral ways: source water, fertalizers, pool chemicals, makeup & lotions and soil & leaves. Phosphate levels vary from season to season as our aquifers change. Our local municipal water, Valley of the Moon Water District and City of Sonoma have virtually the same content of Russian River water supplemented with our local valley well water. Under normal, non-drought conditions, this ratio is typically 85% Russian River and 15% local well water. Currently in 2015, in our 4th year of a drought the ratio is nearly 50/50.
Phospates are a non-toxic mineral that is not tested by the EPA for water quality conditions. They are non-toxic to humans, in fact, all living organisms on this planet require phospates for survival. However, they are very detrimental to pool water quality, as they are the primary cause of algae blooms.
Phosphates are generally not a problem until they reach levels of above 500 parts per billion. Sonoma Valley Well Waters test at an astounding 2,500 ppb in some areas, particularly the Eastside private wells.
Here are some findings from the week of 7/21/15 throughout our valley.
Phosphate tests were performed on source water, not the water content in the swimming pool.
2. Diamond A - 1000ppb. (private residence, community well)
3. Siesta Way @ Barcelona Ave. - 700ppb. (private residence, Valley of the Moon Water)
4. North Castle Road - 2500ppb (private residence, private well, brand new well equipment)
5. East Walnut Street - 1000ppb (private residence, City of Sonoma Water)
6. 2100 Block of Broadway - 500ppb (private residence, private well, state of the art filtration equipment)
7. Hillcrest Drive, Boyes Hot Springs: 1000ppb (private residence, Valley of the Moon Water)
8. Madrone Road, Glen Ellen: 250ppb (private residence, Valley of the Moon Water)
9. London Way, Agua Caliente: 250oppb (private residence, private well)
As you can see, numbers vary throughout the valley. The residences with very high numbers are without a doubt battling algae. At this point, keeping in mind that the water source is the problem, addition of algaecide will not prevent algae as well as preventing water loss.
Tech Tip: watch for leaks and do whatever you can to prevent evaporation. A covered pool slows down evaporation, cuts down on chemical usage and costs associated with algaecides and metal removers.