The Tale of the IntelliChem and ORP


Gold Supporter
Sep 19, 2016
I wanted to share a little bit of learning on my quest to see if I can get an IntelliChem to control my SWG reliably. I'm only a few weeks into this, so just starting to uncover some things. Sorry this is a little long.

So I've been reading here since last fall when we settled on a PB. I made the leap to get the intellichem, mostly because I like the bells and whistles of the sensors and being able to monitor things remotely. I've read all over how ORP is really finicky, and that most people go away from it in terms of controlling their SWG, etc. All of that said, I'm bound to at least give it a shot - after all it's science, right? There's some interesting articles on ORP that validate the technology, and actually also validate many of the solid conclusions of this site such as the relationship between FC and CYA that is clearly not taught by most pool companies. Here's two of them that I've found interesting: this one on ORP vs PPM:, and this one on ORP use:

From what I've read, in order for the IntelliChem to function well, I need to keep my CYA down around 30ppm (way lower than the standard TFP recommendation for a salt pool - I started another thread on this asking for advice on what PPM to shoot for with the IntelliChem in control of the SWG). For me, that probably won't be too much of an issue because my pool is covered unless someone is swimming in it (99% of the time). Right now, I'm slowly working my CYA up since we just opened a few weeks ago, and I don't want to overshoot the number. According to pool math it should be at 20ppm given the amount of CYA that I've added, but in testing it with my TF-100 kit, it's probably closer to about 15ppm (at the same time, this discrepancy could also be that I'm clearly in the range that is too low to be reliably measured). So that's on my to-do list to get it up another 10ppm at least.

So I'm just in the "monitoring" stage right now. No one is swimming. The weather hasn't been warm enough, my gas line is still not hooked up, and I'm waiting on a few things from the PB. The pool is just idling, covered, with a water temp of about 63-64 degrees. I'm testing water every 2 days or so with my TF-100 kit for practice and to understand the inner workings of the pool.

Pool has been sitting right here for the most part:
FC: 2.0 - 3.0
CC: 0.5 - 1.0
PH 7.3 - 7.4
TA: 80 - 90
CH: 150
CYA: ~15

The Problem Presents itself:
Given I have ScreenLogic, I'm keeping an eye on things, and yesterday morning I notice that the ORP value had suddenly dropped down from 726 to 654 (with a set point of 690) to the SWG is suddenly going wide open. Perplexed as to what could have changed since my pool is covered, so I add to my list to gather a set of test results when I got home. SWG runs for hours.

I test when I get home, and I get this:
FC: 6.5
CC: 1.0
PH: 7.4
TA: 90
CH: 150
CYA ~15

I look at the IntelliChem, and ORP is 720. The IntelliChem ORP set point was 690, so it had over-shot. I look a few hours later, and it's now showing 744, so it overshot by a lot. So I sleep on it, wondering why the ORP dropped so suddenly and why the system overshot FC by so much, and wondering if this is what people mean when they say that "ORP is too finicky".​

The Revelation:
This morning, frustration is gone, and my logic hat is back on. I'm looking out the window, and admiring the sunrise. I look at the clock and it strikes a chord with me. Could it be the Sun? I run downstairs to the computer, and what do I see? The ORP value is starting the freefall. My equipment is on the north side of the house, but maybe when the sun is low enough it can hit my I put on my shoes, and head outside. Sure enough. Sun is shining on the Flow Cell...

Now, like any science project, I need a test. I go into the garage, and find a garbage bag. I cover the Flow Cell with a black garbage bag, and note the time as 7:22am.

Here's what happens in ScreenLogic (IntelliChem ORP data) as I do this:

Now I need to go back and validate this against what happened yesterday, apply the learning, and see if there is indeed a pattern:

The limited amount of sunlight that gets through the clear plastic housing of the flow cell is enough to impact the water and completely skew the ORP readings into an unrepresentative sample of the water composition of the pool. The IntelliChem then thinks that it needs to do something (in my case, it thinks that Chlorine is low because the ORP values are low), and it kicks in the SWG. Since the water was never really low in FC, and was probably around 2 - 2.5ppm to begin with, the system is over-chlorinating and takes FC to a level much higher than desired (6.5 in my case).​

In my case, I'm assuming that the logical solution is to find some kind of light impermeable cover for my Flow Cell - I can't readily relocate everything, and I can't deal with the inaccurate readings if there happens to be some sunlight. I laughingly told my wife "duct tape" when she said "so what are you going to do now?". ;)

I'm dumb-founded that this seems to be that poorly thought through.

I then went back to the installation manual (which contradicts itself several times), and while the instructions for mounting the flow cell say "select a suitable location", there's a different section 4 pages earlier in the manual under a heading that says "Installing the IntelliChem Controller" that tells you to install the flow cell "away from direct sunlight".


Mod Squad
LifeTime Supporter
Jul 10, 2012
Tallahassee, FL
Don't you love it when the :idea: moment happens! Well done! For now the bag should work but is there any way you can build a small wall to block the sun from shining on it at all? That will REALLY fix it as it will keep the temp down even more.

Well done sir!



Gold Supporter
Silver Supporter
Yes, it is "science". And it helps when the instructions actually provide meaningful information to utilize said "science"! You still have some organics being chewed by the chlorine, so covered or not, your orp is going to vary. It looks like you have a very nice pool and system!


Gold Supporter
Mar 10, 2017
Los Angeles, CA
Hi DW886,

What a revelation! Thank you for adding a little more clarity to this situation. My PB upgraded me to the IntelliChem from the IntelliPH, and I was disappointed to hear most SWCG members have had less than positive results with it. I'm several weeks from my pool being completed, but look forward to using IntelliChem, and hearing more about your experiences in getting it to work satisfactorily. Thanks again for sharing your experience.


Well-known member
Apr 5, 2017
Plant pot. Buy a plant at the big box store, use the pot to cover the housing. Either direct mount, or engineer a spacer to allow air gap.

should be good for short term, or long