Run Pump Longer or Higher SWG %


Active member
May 30, 2020
South Jersey
From the SWG calculator, to maintain 3 FC per day, I'd need to run my pump for about 13 hours at 100% for the SWG. Is it better to run the pump longer at a lower % for the SWG? I'm not sure if I should be focused on extending the life of the SWG, the pump, or saving cash on electricity.

I just finished a SLAM finally so I'll be letting my FC drift back down and looking to keep it at 5 with 70 CYA. I'm not sure exactly yet how much I lose per day so I may need to drive the pump even longer if I'm losing more than 3 FC per day. Would it make sense to just plan to supplement with some liquid chlorine as well because if I'm losing say 5 FC per day (my pool sits in the sun pretty much from sunrise to 6:30pm per day), it would take 21 hours at 100% to replace....

Thanks! I have learned quite a bit in the past week!


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

This is a problem when you have a SWCG that is way too small for your pool..

In my mind, if you have a single speed pump you should be running 100% and for only the hours needed to generate the chlorine.

It will not matter to the cell, as 1 hour at 100%, is the same as 10 hours at 10%.

There is no right answer here.. Just do what works best for you.


Jim R.


Bronze Supporter
Dec 13, 2018
Orlando, FL
Can you verify your numbers? For your unit, it looks like the chlorine output is 0.8 lbs/day. I calculate 1.9 ppm at 13 hours. It seems the cell may be undersized.

The wear on the SWG is the same whether it is 100% for 12 hours or 50% for 24 hours.

I prefer to run at a lower percentage because then it gives me room to “boost” chlorine if I need to without affecting pump runtime.

Running the pump longer can give you the benefit of more skimming action on the pool. You can adjust your speed to find the same kW per day output at a lower speed for longer hours to match your 13 hours. That way the electricity cost is a wash.

It’s up to you about supplementing with the liquid chlorine. It would be good to have some on hand.


Active member
May 30, 2020
South Jersey
Thanks for the responses. Rick, I got my numbers previously from a different source, but this link confirmed it. Compare and Review Saltwater Chlorine Generator Prices and Features

I have a RC-35 and it says 1.28 pounds and says it is good for pools up to 40k gallons. But my equipment says to keep the pool at 1 to 3 FC at 60 to 80 CYA (Autopilot Pool Pilot). So I'm guessing that's why the RC-35 is "right sized" for my pool. TFP recommends to be at 5 FC at 70 CYA. It's going to come down to how much FC I lose per day.

I have a single speed pump so I'm stuck there.