Re: I Just Did An Iron Treatment
Chem Geek,
Thank you for the reply.
Last night I got the pool to hold 6 ppm chlorine by 6pm at a CYA of 30, it had stopped dropping. This was acheived at power level 3, max for the SC-60, at 100%, but still when I switched to ORP the measurement came in at only 522, it held there to 9 pm, potentially dangerous as you will see below.
At that point I think it had something to do with perhaps too much sequestrant, as you mentioned, it already had a maintenance dose of the old Omni stuff, and then a full bottle of Jack's Magic The Purple Stuff, what I should have done perhaps was just to add a maintenance dose. This I think caused the excessive demand for chlorine. I also went for a swim somedays ago without checking the ORP when it seemed to settle around 4, of course it dropped overnight and that is when I knew I had a problem plus the CYA fell again. Well I got a bacterial foot infection presumably as the ORP was too low and was prescribed antibiotics for that, but of course it could have been something else.
Thank goodness I can measure the ORP otherwise I really would have been lost, I actually rarely use it using the SC-60 at power 2 and 60% feed. Anyhow last night I added 9 bottles of Walmart's 6% chlorine(1638 ozs or 79 ppm chlorine), holding the pH to 7.2 by adding acid, I did this a bottle at a time until I got the ORP over 700. The ORP rose to 712, then I set the ORP controller to 800 or if you like a 100% feed, the ORP rose to 748, perhaps higher in the middle of the night, in the morning I switched the ORP feed off as the pool had about 60 - 70 ppm of chlorine, not sure exactly as I had dilute the sample just to get a reading 19 parts water 1 part pool water. It is currently sitting at around 722 at 9:30 am. No iron precipitated out and the CYA is holding at 30, which is where I think I will leave the CYA level.
Now I am letting the pool down to FC 5 naturally (no additives) and see if the ORP holds in the 700+ range overnight and in the 650 area during the day, if not I will have to drain as this 700+ level is what it has always acheived in the past overnight. I hope this 139 ppm of chlorine in total has solved my issue.
What I learnt from this experience is that an ORP meter as a measuring tool is invaluable if you value your health and safety, and do not add more than a maintenance dose of sequestrant if you are already maintaining the pool, perhaps a little more if you notice any precipitation. I really think it is worth having an ORP meter, be it built-in or portable, particularly if one has children or grandkids like me who may swim in a pool, but of course it does not work very well at a CYA of 45+, and not at all at a CYA of over 50, so for those persons with high CYA it would useless.
Well I hope my unfortunate experience with iron treatment "without draining the pool" is helpful to some. Someone might want to apply cautions to the "Ascorbic Treatment to rid Pool of metal stains" post, as I have read other posts where they develop algae blooms, etc. after the treatment. Considering my pool was very clean before in regards to FC and CC issues, and I caught the issue right away as I kept feeding the pool with Chlorine I was very lucky, plus I have 15 years of experience maintaining my pool. If I just read the "Ascorbic Treatment to rid Pool of metal stains" and added a lot of chlorine I might have walked away or gone for a swim, which I did, not knowing that there were other issues. Adding perhaps a note on not adding too much sequestrant, falling CYA, not to swim until both FC starts holding, and waiting a day or so to make sure CYA holds for at least a day might be a good idea.
Update at 2.22 pm: The ORP is still holding in the 690s, the FC is in the 20s down from 60 to 70. But what is really interesting is that the pH drops 0.05 about every half hour, I am adding borax to compensate; I started with zero borax in the pool so not an issue. But I think that is better than the problems before and when I do start generating chlorine maybe tomorrow I think that will balance itself out. It is very windy today up here on the mountain at 1000 ft at 20 -26 MPH , and very sunny, the high UV is fortunately burning off the chlorine but with not too much effect on the ORP measurement. Chlorine and acid feed still turned off. CYA is still smack bang on 30 so that issue is resolved, finally light at the end of the tunnel.
Update 4.55pm: CYA still 30 (no Thiosulphate added) and 32 (with 2 drops Thiosulphate added), FC 22, pH has stopped falling and rises by about 0.05 every hour or so. No chlorine feed, acid feeder now turned on and set at 7.2. ORP about 684.
One advantage of this whole mess is that it looks so clean in the odd moment that the wind stops, nearly like new, and the rough pitted area on the wall feel beautifully soft. It even seems to have completely removed most really stubborn tannin stains put there years ago (although each treatment does remove some) when we had a tree growing near the pool that dumped lots of leaves, since chopped down. So maybe we should title this thread "Stupid Old Grandpa Solves Ancient Tannin Stains By Doing Something Really Stupid", my grand kids would like that title.
Alls well that ends well at least I hope it is.
Aloha and thank you for your help.