SWG, ORP level, and chlorination relelation question

[RAH123]

I know this is an old thread but as many others seem to have been doing, have been trying to use ORP to control my pool Chlorine with a SWG, one reason I would like to do this is because of the fact that a: my property is rented out during the summer and b: I have an Abri (pool shelter), when the pool is covered it seems the chlorine does not "burn off" so will accumulate if not uncovered for a period, which does happen, if the SWG is left on a timer.
I, like the OP had the issue where when my SWG was turned on the ORP level actually dropped! after MUCH reading of ORP, SWG and anything I could find on the subject I saw a couple of posts saying that with a saltwater pool and SWG you need s gold ORP probe instead of the more usual platinum one as the hydrogen generated COULD affect the ORP readings although I could not seem to find any "official" documents that stated this.
I decided to try this anyway and after a bit of searching found an ORP probe with a gold electrode and fitted this to my system, the whole thing was instantly better and more stable, ORP goes up and down as expected during the course of the day and night, when the SWG is turned on the ORP No longer drops and although I accept that it may not be perfect it is definitely a lot better, I do find that the ORP also changes a bit with pump speed, when I run the pump slowly at night the ORP level drops slightly and exactly the reverse happens when I speed the pump up.
I also had a few other issues with fluctuating readings when I first installed the ORP controller but most of these were solved by bonding and the installation of an anode so I would also advise checking these when installing an ORP controller.
I am sure there is more to find out about all this but I do at last seem to have a system that is a lot more useable than before Hope this helps
someone!View attachment 420745

Just a small update, after about a week with the ORP probe with the gold electrode instead of platinum my system does seem to be at a state where I am happy leaving it to do it's own thing, which is the first time I have been able to say that!
The ORP readings fluctuate quite a bit through the day which I am assuming is down to my CYA levels which are around 50%, in the day I think the FC bonds with the CYA so the readings go down. I have a STA-RITE SC75 which has 3 power levels, 33%, 66% & 100% I used to have this set high as the levels did not go up when it was running so I ended up with a very high chlorine level but low ORP, now I have it on 33% and my set point on my controller to turn this on is at 650mv, on this setting the SWG has been on for about 6 - 7 hours which equates to about 2 hours of chlorine generation which seems to keep my chlorine level according to the little test strips just about perfect! Today it is a bit cloudy so my ORP has not dropped very much which I think is correct.
I have a smallish pool, about 7m x 3m and also have a retractable pool shelter.

Hi, I've got a 15k pool with SWG, ORP and PH Probe (intellichem) and also clearcomfort, and an automated poolsafe pool cover. I've found when I run my IC40 SWG at 100% to bring up my ORP it drives the ORP lower. This has been going on for years and i saw your post. I've heard some say it's due to chloramines, and lately have been seeing those saying SWG generates hydrogen and the platinum tips are the blame and i need a gold ORP. Since you said you found one that worked for you can you post what one you bought? And it works with intellichem from Pentair?
Not sure how often people shock their pool. But I don't have more than 0.3ppm combined chlorine and i had to shock my pool once in 4 years and never had an algae problem and use the intellichem. I don't use clear comfort (AOP system) to almost eliminate chlorine, i use it in addition to my SWG and intellichem and it seems to keep my salt cell from ever being used except during high bather loads. Even intellichem seems to work with the platinum ORP sensor but my FC usually is between 1 and 4ppm and my CYA I keep around 25. I did try and clean out my salt cell after about 4 years of use, and noticed it's spotless so maybe the automated reversing terminals or whatever seems to be working and my acid clean didn't fiz and the plates looked clean anyway. According to intellichem and the history it seems my salt cell is on about 5% of the time. Would appreciate knowing what probe you are using in place of the platinum one, as that should give me tighter control over FC (Yes i know ORP doesn't tell you FC, but it will give me better control over FC range relatively speaking depending on many other factors, etc.). Everyone seems to argue that ORP doesn't tell you FC. But it's not intended for that. ORP is intended to tell you the potential to oxidize, and other than the platinum tip and the SWG interaction somehow, it does a great job of telling you how well you can oxidize stuff. Yes people argue FC stays the same and PH rises and the ORP drops, but that's because the ability to oxidize has reduced with the increase PH. Anyway hope you are enjoying your system as much as me!

 

[needsajet]

You might want to consider drop-based FC testing which is reliable for FC management. With your size pool and SWCG providing the chlorine, it's very likely you'll have less total effort than managing ORP sensing. CYA is a necessity for Trouble Free Pool Care (TFPC) and ORP with CYA is troublesome due to ORP sensor contamination.

IMO, abandon ORP sensing and raise CYA to 60-80ppm. Monitor FC daily for a while until you have it dialed in, then adopt whatever frequency of testing meets your needs.