Phosphate levels

[gpeete]

How important are phosphate levels? Do I need to be concerned or is this another way to sell unneeded chemicals?

[PoolDoc]

Phosphates can contribute to algae growth.

BUT . . . if you're doing everything else correctly, phosphates usually don't matter. Also, most phosphate removers cause problems with cloudiness, and the cloudy mess can be very hard to filter. In the pool shown below, phosphate remover was added to the spa. The entire pool became cloudy -- combined circulation -- and it took 2 weeks, before it was crystal clear again.

[chem geek]

Think of algae growth as being the flames of a burning wood pile. Think of chlorine as water trying to douse out the fire. Think of wood as phosphates (and nitrates) or fuel for the fire. Though having wood in a fireplace means that with a spark one could start a fire, if the wood is constantly getting spayed with water, then that spark will never take off into a full fire no matter how much wood there is. So long as you maintain the proper chlorine level relative to CYA, then you are able to kill algae faster than it can grow, regardless of phosphate level. Algae are limited in their growth not only by nutrients such as phosphates and nitrates, but also by sunlight and temperature.

Now, that said, a pool with very high phosphates, say 3000 ppb or more, will be very "reactive" so IF you let the chlorine level drop too low then the algae grow close to their maximum rate. Nevertheless, this is still only a doubling in population every 3-8 hours.