Pool barely has any FC; Jacuzzi says it is phosphates

[Rancho Cost-a-Lotta]

Do you have a variable speed pump? The salt cell that you have is designed to be installed as the highest component of the plumbing system. This means that all air and gases accumulate at the top of this cell. Having had this same style, I found that my cell was filling up with air when running at low speeds and the plates were becoming exposed. Likely, the system was also shutting down due to lack of flow when running at low speeds. If you have a single speed pump with sufficient flow, you likely will not an air bubble at the top of the cell. Just mentioning this as a possible factor to the inconsistent generation of chlorine.

 

[mas985]

Is the cell clean and free from scale?

 

[edschwartz]

Yes, the cell is visibly clean and free from scale. (Fun fact: The technical support rep did not ask about this or CYA levels before jumping to the phosphates conclusion.) No service lights are on. I also do not have a variable speed pump.

Thanks for all the ideas.

 

[Mdragger88]

Time for ….

 

[edschwartz]

So I have good but unexpected news. Since I put bleach into the pool for the OCLT, the pool has stabilized to ~6 ppm FC. It never dropped back down to zero. The only explanation I can think of is that there was a small amount of algae that I killed when adding the bleach for OCLT. The overnight chlorine generation test produced less than expected... but maybe with (0.5 ppm) rounding error it's not that far off?

For now my plan is to keep an eye on the FC levels...