Can someone smarter than me explain this oversized sized cell economics?


Jan 11, 2016
Los angeles, ca
I was wondering how big is too big? So I wanted to buy an oversized Pentair IC-60 for my 13,000 gallon pool. I would run it at a low output to increase its 10,000 hour lifespan. But then I read this from Chemgeek:

There is one side effect to oversizing a unit which is that when it is on it is outputting higher FC levels (out of the returns) and this would be exacerbated at lower flow rates. The IC60 at 0.56 ppm FC per hour would be 3.4 ppm FC incremental out of the returns in an 18,000 gallon pool if the turnover time were 6 hours and in a smaller 7500 gallon pool it would be 1.3 ppm FC per hour so with 6 hour turnover that's 8.1 ppm FC. So there are some practical limits to oversizing especially in smaller pools and longer turnover rates. Since the IC40 is still fairly efficient, it may be a more practical choice in smaller pools with 30% lower FC levels coming out of the returns. (Economics of Saltwater Chlorine Generators)

Is he saying that the IC60 will over-chlorinated a small pool? But aren't there variable output settings on the IC60 (2%,4%,6%, 20%, etc) that can account for that?


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
I would run it at a low output to increase its 10,000 hour lifespan.

The 10,000 hour spec is generating time. When generating it only has one output. There is no “low output”. The ICXX cycle time is 300 seconds. The % sets how much of every 300 seconds the cell generates for.

When buying a very oversized cell you are making the bet that your cell will live a normal life and not die prematurely due to reasons other than the plates being depleted. We see some folks winning and some losing.

With a very large cell you have a few tools to not over chlorinate your pool:
  • Adjust generating %
  • Adjust pump run time
  • Power cell on/off using automation if you want to run your pump longer then run your cell every day


Mod Squad
Gold Supporter
TFP Guide
Jun 16, 2019
While upsizing always works in your financial favor (IC40 to IC60 costs 20% for 50% more lifespan), I do believe there is too big. At some point, the electronics in the unit will fail and you will lose whatever expensive plate coating is left. Now. It only has to last 20% longer than the 40k unit to break even as that is what you payed, so it doesnt have to last it's full life to still be worth it. But at *some* point, you are buying a unit that will fail before its ready.

At 13k gallons the IC60 is a 4.6X unit and we advise 2X. The IC40 is a 3.07X for you. I would take a 3X in a heartbeat of one was available for me. I would strongly consider the likelihood that anything larger than that might not make it.

If lightning hit nearby, or there was a power surge on year 2 it could ruin 10+ years worth of SWG.
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