Intellichlor IC 40 and FC levels

[espejo]

On page 10 of the installation brochure for Pentair's IC40, it references the optimum pool chemistry for salt water pools and the reference to free chlorine caught my attention, It states, "Free Chlorine: 2.0 - 4.0 ppm. Above 4.0 ppm may cause corrosion of metal components".

I currently have the Stenner with a CYA of 50 and according to TFP my minimum should be 4.00ppm and my target is 6.0ppm. I regularly keep my FC at 6.0pm and my water looks great. However, it has only been 7 months. Am I causing corrosion to metal components as the Pentair manual states? I most concerned about my pool heater but I believe the heat exchanger is stainless steel so maybe this is not an issue.

Thoughts?

 

[JoyfulNoise]

This question often comes up a lot and what you have to understand is that many of the user manuals are written in the context of the pool industries "recommended guidelines" of which TFP has debunked many of them. The pool industry has always told pool owners that all you need is 1-4ppm FC, FULL STOP. They completely ignore the FC/CYA relationship and this is why so many pool owners have so much trouble with their pools.

This is the mantra you need to put into your head - "Metallic corrosion is PRIMARILY controlled by pH"

pH is the determining factor for metal corrosion as it is low pH that strips away the protective oxide layer (passive film) that forms on metal surfaces. Now chlorine and chloride will enhance certain forms of corrosion and inhibit the formation of certain types of passive layers (eg, chrome oxide passive layers on stainless steels are inhibited by chlorides), but the initiation and rate of corrosion is completely dominated by pH.

So, as long as you keep your water properly balanced with respect to pH, your metal pool parts will be fine.

Galvanic corrosion is another issue, but again it is rarely a problem in properly balanced pool water. As insurance against galvanic corrosion, one can attach a zinc or magnesium sacrificial anode (buried in moist soil) to their bonding wire and that will help to protect metal components. But again, it's all dominated by pH.

 

[espejo]

Thanks. Very helpful.