Chlorine Always High

[VenomPool]

This is the second year with our pool, and I've always learned the that it takes three years for perfection. First year you learn, second year you adjust, and third year you perfect.
We have 7,610 gallon Fiberglass Pool. We are using a variable speed Pentair, with an IC20 SWG, with a single cartridge Pentair Filter. I was running the system, 24 hours last year to keep our FC up, and never could find at happy spot to keep it around 3 (it would go as high as 10 at 30%, and then 8% it would be 1 or 0).
In order to keep the SWG active and working, I found out that the minimum speed that the pump would have to run was 1000 RPM (roughly 40 GPM.
This year I'm running 8 hours, 1 hour at 3000 RPM from 8-9 a.m. (to skim pool), 9 a.m. - 4 p.m. - 1950 RPM, and then 500 RPM from 4 p.m. to 8 a.m. Using Pool Math, it was recommending running the SWG at 80%, and the FC was way high. I've backed it down to 30% and I'm still have an FC of around 8. What am I doing wrong? Did the pool builder size the SWG to large?
Just as another note, my pH is 7.4, CYA is 60, Alk is 110, no other issues with water or algae.
Thanks in advance!

 

[thetekgeek]

How are you testing to get these numbers?

Dialing in the runtime and % output combination for a SWG is a process sometimes. Make small changes and test 24 hours later, then adjust again. Do this over a span of a week and you'll start to see some consistency.

Keep in mind as we get deeper in the season your chlorine demand and needs will increase, so your % output or your runtimes will vary through the swim season.

Also, FC @ 8 with CYA @ 60 is perfectly fine and safe to swim in. See this article - The Free Chlorine and Cyanuric Acid Relationship

 

[VenomPool]

I'm using the DPD test from the Taylor Salt Test Kit. I've always use strips to verify and I'm getting a similar reading.

 

[proavia]

Welcome to TFP!

Are you using the FAS-DPD (R-0870 and R-0871 reagents)?

Toss the test strips out - they are inaccurate and inconsistent. They also degrade rapidly once opened.

And FC of 8 with a CYA of 60 is perfectly fine.
Set the SWG to keep FC on the high side of the target range based on your CYA.
FC/CYA Levels

 

[VenomPool]

I have the the R-0871 reagent, R-0870 and R-0003 in my test kit

 

[proavia]

I have the the R-0871 reagent, R-0870 and R-0003 in my test kit

Perfect!