IntelliChem pH values way off?

[jtech1]

I have learned to not pay too much attention to the ORP values based on everyone's feedback on here and a month of experience now... but during that time, the pH has been pretty much dead on accurate as compared to my test kit values. Up until today. We got 1-2" of rain from Arthur today. All of a sudden, the IntelliChem pH reading dropped from 7.5 to 6.5. I thought may be it was pulling water from the top of the pool (skimmers) and the rain water is acidic, so I changed it to pull from the main drain, and it still shows 6.7 a couple hours later. I tested with my test kit and it actually reads 7.8 (was 7.5 with test kit yesterday). I have not added any chemicals for the last couple days. Only SWG running. TA is still dead on at 80.

I am going to believe the test kit reading... although, after 2" of rain, I did expect the pH to be slightly lower... not 0.2 higher. But I'd liek to figure out why IC pH dropped by 1.0 instantaneously and has stayed near there for a few hours now.

I have attached the IntelliChem history graph... is there something specific that may have caused this? Or am I now going to have to lose confidence in the pH reading from IC also... meaning I really wasted $$$ on this. I don't have the pH canister hooked up yet, so no acid was dispensed... luckily... since it would have done so incorrectly and dropped my pH well below where it should be based on this false reading.

Edit: Also notice the ScreenLogic error on the graph below... IC reading was 6.5 at the drop and is 6.7 as I write this, but the graph makes it look like 6.9. The graph is frequently wrong, both in history and current values.

 

[JasonLion]

There are several possibilities. I would start by cleaning the tip of the PH probe and double checking that it is properly connected to the IntelliChem. If that doesn't help, try power cycling the IntelliChem.

Another possibility is that some concentrated chemical was put in/got into the skimmer. For example a trichlor tablet or CYA in the skimmer would do that.

 

[jtech1]

Yesterday I cleaned the probe tip with dish detergent solution and soft tooth brush. Checked connection. Restarted IC. Reading is even lower now, 6.1. Test kit shows 7.5. I am going to try the second cleaning method in the manual... the acid/water solution, today. If that does not work, I am guessing I need to go to Pentair for a replacement probe... I guess I am not surprised... this is just another in the list of failed Pentair equipment I have had... globrite light, color cascade light (two different ones; from moisture getting in housing), and now this.

 

[JasonLion]

How old is the PH probe? The normal lifetime of a PH probe is around two years.

 

[jtech1]

Two years of use or shelf life? I just bought it end of last year. Looks like it must have been sitting on the shelf a while. The probe box says return to Pentair if after 4/14, which I did not see when I installed it last month. The tip was still wet when I removed the protective cap.

 

[JasonLion]

They wear out even when not in use, though not as quickly as when they are in use.

 

[dradam]

I just started having the same problem you are having. My Ph was rock stable for the last 2 months and suddenly it is whacky and flow dependent. This is the second season with this probe. I had a similar problem early last year when under warranty. Turned out it was not the probe, but the cable so you may want to replace that as well.

Good luck.

 

[jtech1]

Interesting.. I came back to give an update and saw your post, dradam. I got a new pH probe (just pH... even though my ORP probe also said to return to Pentair if after 3/14, they said their new policy is NOT to replace them unless they are bad... my ORP is all over the place, so I don't know if it is bad or normal... but, oh well). Installed the new probe and the pH level is still bad. I need to call again mon and see what the next step is. I may try to swap the cables today to see if that fixes it as it did for you.

 

[jtech1]

I swapped the cables and the pH looked good again. Going to get a replacement cable. Not very often you see a cable fail like that. I would probably not buy IntelliChem if I had to do it over again. May be even not buy Pentair Automation... but that's another thread.