I just did an iron treatment

[smallpooldad]

I just did an iron treatment to my 10,000 SWG pool last Friday and Saturday with 1.75 lbs of AA and 32 oz of Jack's Magic The Purple Stuff.

It took approximately 60 ppm of liquid chlorine to get it to hold at a FC of 4. I checked, every half hour and then later hourly all day Saturday before it would hold at 4 FC, adding acid as necessary to keep it 7.2. At no time did I allow the the chlorine to above 5. This is in a pool with a CYA of 40.

I think the 2.5 ratio might be good for citric acid, I am no chemist so I am guessing here, but you would need to take into account the ascorbic acid demand that I experienced.

So it seems from experience with AA only and 32 oz of Jack's Magic The Purple Stuff, I know nothing of chemistry, that about 30 - 34 ppm of chlorine will neutralize 1lb of AA in a 10,000 gallon pool.

It would be interesting to know what you actually end up using and if it correlates with my experience. If my experiece is correct you would need 60 to 68 ppm of chlorine just to neutralise the AA plus extra for the Citic Acid.

Let us all know the final tally so you may help others.

Hope this helps.

 

[chem geek]

Re: Chlorine Demand from Ascorbic Acid Treatment

I've done the ascorbic acid treatment and it didn't require anywhere near that amount of chlorine to get readings again. If someone uses a chlorine neutralizer, then that has to be factored in. If they use a lot of PolyQuat 60 algaecide, then that also creates a chlorine demand. And if they use some types of metal sequestrants, then they can consume a lot of chlorine though that's usually a much slower chlorine demand. It's also possible that during the period of time when the FC is zero that bacteria start converting CYA into ammonia -- hopefully having PolyQuat in the water at least slows that down.

 

[smallpooldad]

Re: Chlorine Demand from Ascorbic Acid Treatment

Chem Geek,

I do use Algaecide 60 but it was being maintained at a maintenance dose so would that make a great difference?

In addition this being near the middle of the year the UV is very high (around 11) at this time of year, near its highest level at Latitude: 21° 19', North, that to might be a factor. But prior to the treatment the FC was 5 and the CC = 0. The treatment was done at dusk around 7 pm (Sunset: 7:15pm) and the chlorine added back the next morning at around 7 am (Sunrise: 5:49am), a little after dawn. Pool temperature was around 84 F.

I did use Thio-Zine to neutralize the 5 FC, it is possible I added a little extra maybe 2 oz.

I just thought of this the CYA did drop from from 40 ppm to 27 ppm, I thought it was from adding all this chlorine but could it have been that bacteria were converting it to ammonia and would that account for the large difference in use of calculated versus actual use of chlorine?

The mystery thickens.

Hope you can help us out.

 

[chem geek]

Re: Chlorine Demand from Ascorbic Acid Treatment

The maintenance dose of PolyQuat wouldn't likely have done much. It's larger doses that tend to use chlorine up fast enough to notice. Maintenance doses have a much smaller chlorine demand spread out over the week when you need to add more PolyQuat.

Yes, if your CYA drop was real then that could have been the start of some bacterial conversion of CYA into ammonia and would explain the higher chlorine demand.

We can't always figure out what goes on in every pool and mostly just do educated guesses based on what we see in many pools plus, if known, the chemistry of what may be happening. We still don't know about what causes the CYA drop over the winter when there is still chlorine present nor exactly what happens when the CYA drops with no FC but there is no significant chlorine demand. Some day, we may figure out these mysteries and have solutions.

 

[smallpooldad]

Re: Chlorine Demand from Ascorbic Acid Treatment

Chem Geek,

I forgot something and maybe this the reason for my higher than normal usage.

I did maintain a weekly maintenance amount of HEDP from OMNI (no longer available), if by adding the 32 oz of The Purple Stuff did I create a situation that set itself up for a high chlorine demand. Question: And if I did should I have added merely a maintenance dosage after treatment?

So my situation may indeed be different from NHPool's.

I am beginning to think that it was this and a combination of the CYA dropping, the CYA drop may have occured in NHPool's case you would need to ask him, that created this large demand, what do you think.

I hope I am understanding this correctly.

I looked at your post here and I think this is what happened but my water was just slightly cloudy. I thought that was the chemicals.

http://www.troublefreepool.com/it-can-happen-to-anyone-zero-chlorine-cya-ammonia-t10974.html

Well at least I will know for next time.

Thank you for all your help

 

[smallpooldad]

Re: Chlorine Demand from Ascorbic Acid Treatment

Chem Geek,

Well it looks like I have the same CYA drop issue, but maybe not so bad.

The pool looks clear and shiny, took a sample of water and it looks clear, and there seems to be no ammonia smell.

Three days ago the CYA measured 27 down from 40 before the iron treatment, I added 7 parts Instant CYA and 6 parts of the powder to get it back to 40 today it reads 30.

The chlorine had a hard time holding at FC 4 although there was no CC, but I had to turn my Pool Pilot SC60 from power level 2 at 60% to Power Level 3 at 60% just to get it to hold and it still went down to FC 3.

The other day overnight I set it to ORP at 700, it never got above 612, normally it will go over 700 by just a little, even though the FC read 9. At 2pm today it reads 522, I know that sunlight has an effect on the reading but the worst I have ever seen it in the daytime is 622, normally I do not use the ORP function except for a monitoring device unless it reads unusually low then I might let it run overnight, but now I think I need it.

So I upped the CL to 6 with 6% liquid Walmart chlorine, the acid was thank goodness already at a pH of 7.2 as I was going to keep it that way for the week. I have not tested for Ammonia, I need to get a kit at the pet store. I am planning on running the PoolPilot in ORP mode until I get a decent reading 24/7. The ORP half an hour later is at 558.

I normally only do an Iron Treatment with a full drain with no problems, why oh why did I do it without the drain, aaaahhhhh.

Below is my current setup any recommendations would be appreciated, and should I add CYA if it drops below say 30, or 25, or 20, or should I up it to 40 and increase my chlorine level to say 7, although I think by setting it in ORP mode it will push it higher?

With numbers below do you think that if the ORP mode pushes the chlorine numbers above 7 the pool will start to get iron precipitating out, although there is a lot of sequestrant in the pool? Or will our current high UV of 11 offset that effect? I am leaving the cover off I think that helps with any ammonia, or does it?

This is about an hour later from when I started this, noticed something strange the pool is producing little white flecs about the size of calcium before one puts it in the pool, maybe a little smaller. If I put it in my hand they dissolve, is this dead bacteria or algae? Or am I creating a new life form, or is it producing fluffy calcium hypochlorite sediment, weird as my grandkids would say?

It is is now nearly 2 hours later and close to 4pm and still the ORP is only around the 550 mark, grrrr, looks like chlorine dropped to 5 from 6 so added more liquid.

2 1/2 hours later, ORP has not shifted, am beginning to think that only a standard shock at 12.2 FC or a Yellow/MustardShock will work, any opinions? I am aware that the ORP is tied up by the CYA so I will wait till 11pm (Hawaii time), 5am (Eastern Standard time), and then if no joy go for the shock unless you write back otherwise, I realize you may not see this post before that time. But I feel that upping to Shock level the FC will quickly get eaten up by whatever it is that is affecting the CYA and lowering the FC, so it will not stain I hope and if it does I will do it again and drain like I usually do.

Aloha.


Initial
Measured pH 7.2
Total Alkalinity (ppm CaCO3) 130
Free Chlorine (ppm Cl2) 6.0
Cyanuric Acid (ppm CYA) 30
Calcium Hardness (ppm CaCO3) 375
Total Dissolved Solids (ppm) 3300.0000
Total Sulfate (ppm SO42-) 0
Total Borate (ppm Boron) 0.0
Total Ammonia (ppm Nitrogen) 0.0
U.S. Gallons 10,000
Temperature (oF) 84

Total Chloride (ppm NaCl) 3056
Carbonate Alkalinity (ppm CaCO3) 120.5
Langelier Saturation Index (LSI) -0.11
% HOCl (vs. Total Free Chlorine) 1.9%
OCl- (as ppm Cl2) 0.070
HOCl (as ppm Cl2) 0.112
Calcite Saturation Level (CSL) 0.58
Calcite Saturation Index (CSI) -0.24

 

[chem geek]

Keeping the pH from getting too high is more important for preventing metal staining than the higher FC level. Having sufficient metal sequestrant is important as well.

I wouldn't worry about figuring out the true source of the chlorine demand at this point. There wasn't enough of a CYA drop to be definitive -- anything within the error tolerance of the testing isn't going to give us any answers. It's possible The Purple Stuff increased chlorine demand -- I don't know.

You don't want your CYA to get too high given your ORP system, but as to whether you choose 30, 40 or 50 ppm that's up to you and the chlorine usage and ORP stability you find -- i.e. it needs to be determined experimentally for your pool (perhaps you've already figured that out). If you are losing your chlorine during the day, but overnight it seems to regulate or hold much more readily, then the CYA probably does need to be higher (40-50 ppm).

It also sounds like your ORP system is, quite frankly, not doing a very good job maintaining a consistent chlorine level, but check your overnight chlorine demand to make sure there isn't something else going on. At this point, this will just let you separate out chlorine demand from sunlight vs. that from other sources.

 

[smallpooldad]

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.

 

[chem geek]

Re: I Just Did An Iron Treatment

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.

Other than using ORP for automation of chlorine dosing, I don't understand what you are saying here. ORP is not a measure of the health and safety of the water. It is a rather finicky, inconsistent measure of the net oxidation potential of all chemicals in the water. It's quite possible that some of the sequestrant agents you are using affect the ORP reading in a negative way, but that has absolutely nothing to do with the sanitation of the water. It is the hypochlorous acid concentration in the water -- something you can control and measure with the FC/CYA ratio -- that is relevant for sanitation. If you were to add non-chlorine shock (MPS) into the water, the ORP would shoot way up, but the rate of sanitation would only rise a small amount as MPS does not kill pathogens nearly as quickly as chlorine.

 

[smallpooldad]

Here I think we will have to agree to disagee.

Although yesterday I had a FC reading of 6, and a CYA of 30 by setting my SWG to its normal output at power level 2 and 60%, it would not hold, I had to set it to level 3, and 60% or higher just to hold the FC. Switching it to the ORP, which I do not use to control the pool, I use the power settings so my FC never drops by more than FC 0.5 overnight, it advised me that the ORP measurement which is normally around 650 was in the lower 500s. By using this information after sunset, I put 182 oz of liquid chlorine at a time in until I got to 700 I was able to overcome my problem fast by adding exactly 9 bottles, or if you prefer the near correct amount saving me both time and money. As you are aware it gives very inaccurate readings in the day and much better ones at night (but agreed not perfect). That is why as you know it cannot be used to control outdoor pools with CYA or so I am advised, and that makes sense.

I agree with you that one should not control ones pool with an ORP controller as it does not give safe readings due to fluctuation especially when combined in sunlight with CYA but use the power settings which I do 99.9% of the time but in this case it did help "health and safety". "Health and Safety" is not just driving well but making sure you have enough gas, oil and water, I think this a good analogy to this issue. If your oil indicator shows low oil it does not mean that you need to stop immediately but certainly one should attend to the underlying issue as soon as possible, yes having a dipstick is great as well, but having an immediate notice is better.

I think you might be a little wound up about this issue as people constantly bombard the site with "Why cannot I use an ORP controller to run my pool", and "They use ORP controllers in Germany" but that is not what I am getting at here, and yes I agree those are crazy ideas often let lose on a misinformed public. In this case I might still have gone for another swim but I still believe that might have been dangerous. In 99.9% of cases I agree with you it is a fairly useless "Rich Man's Toy" but in my very rare case for the first time since buying it over 3 years ago it did play an important part in guiding me to a healthy and safe solution. So I hope that you and I can agree to disagree, although I agree with you more than disagree 99.9% of the time.

But my main concern is that issues such as dropping of the CYA and watching to see if the FC drops overnight should really be addressed in the "Ascorbic Treatment to rid Pool of metal stains" post, merely as a cautionary advisory. While it most probably happens infrequently, it does happen and that is a health and safety issue. What opinion might you have regarding these concerns?

 

[chem geek]

The ORP may have been measuring the presence of organics in the pool that could be reduced by chlorine, so in that sense they could have predicted the higher chlorine demand. However, you could easily determine that via an overnight FC drop test. Just as a higher ORP in the presence of MPS does not mean that the water is that much more sanitary, a lower ORP does not necessarily mean that the water is unsanitary nor even that there is a higher chlorine demand, though in your particular situation this time it did.

So again, ORP isn't about whether it's sanitary, but can be useful for process control and in your situation this time was also a predictor of chlorine demand. I'm not saying it doesn't have any value -- just that you can't look at an absolute ORP reading and say, "well, it's 650 mV so I know it's sanitary". Different ORP sensors from different manufacturers measuring the same water often have wildly different ORP readings. In a study of 620 samples from 194 pools, comparing ORP readings from a portable Oakton ORP measuring device vs. the built-in ORP controllers in many of the pools, 30 out of 130 (23% of those that had built-in ORP controllers) were off by more than 100 mV.

 

[smallpooldad]

Well I agree with your statements . What I am trying to say is that I know the pool's good numbers and I know the pool's bad numbers from runnning this piece of equipment. When I have looked after it well, the chemistry that is, and when I have been sloopy and lazy. Seeing the numbers I saw on the meter but not on the tests, which looked fine, strongly indicated to me where the issue lay, as I had seen this before, with a lack of enough chlorine and that something was either going to happen or was happening.

True it could have been something else but the number was so bad that I knew better than to risk a second swim and that as nearly always chlorine "my one true love" would most probably save the day, or at least that is where I should start.

But look at it this way the average Joe pool owner looks at his FC reading in the morning, well I can get it to hold at 6 even though the power had to be pushed up from 50% to 90% and the CYA is fine, so when I get back home with the kids in the afternoon after piano lessons we will swim. Get back home pool looks ok, everyone jumps in a next day everyone gets a little sick with something.

Pool starts to look bad next day, calls poolman or goes to pool shop they test water, he/she states the pool power had to be turned up to get it to work, oh they say your cell is going here is a new cell, oh dear it will not fit they changed the design, no problem the owner will come up in a couple days after he docks his 62ft yacht in Tahiti, and flies his private jet back to LA, oh dear I forgot he has to go to the SWG junket in Vegas, what's it called Harry, Harry calls back "Salty Babes Are Us", is a week ok it will take us that long to write out the bill, and so on and so on. Reading from an ORP with known good and bad numbers regardless of whether they vary from meter to meter may have avoided this, as it did in my case. Agreed it is a very limited tool and not what it is cracked up to be but it does have it's merits for the less scientific among us, if trained how to exact its hidden talent.

True it cannot tell me whether it is sanitary or not but it can forecast impending gloom, horror, and devastation, or at least all is not as rosy as it seems.

So I agree, that should I get a new ORP sensor I would have to relearn a good reading versus a not so good and set a standard. Here is most probably the issue with doing a study of the 130 sensors, some of the operators had set a measure as to what is good and what is bad. Some were operated by people who either did not care or took no time to create standard by which to measure and at other places the operators changed so frequently that they never were there long enough to aquire a working understanding.

The usefulness of the ORP is directly related to the experience of the operator and the help you and others give to them on this and other websites, etc.

Example my own older daughter used to help out down our hill at the local municipal pool, there she was put in charge of pool sanitation every Tuesday afternoon/evening and Saturday morning, her friends covered other days. She was I think around 9 years old. As my daughter would say hello. Not an experienced ORP expert.

So I agree in the wrong inexperienced hands it is worthless but in more experienced hands it can act as an early warning system even if the readings are off.

But frankly as I stated I think we will have to agree to disagree and leave it at that. I think we both know where we stand on this and move on, you are welcome to make an additional comment(s) but for me this has will be my last post on the subject of ORP.

As stated what concerns me more is that this does not happen to anyone else, concerning the cautionary note do you feel that it has merit, or not, and that it could be added to the "Ascorbic Treatment to rid Pool of metal stains" in some form or another, perhaps better written than the one I wrote by you or Jason Lion?

 

[chem geek]

I understand. Well as for the cautionary note, we know that some metal sequestrants have a high chlorine demand, but presumably the ones we recommend with HEDP don't or it's fairly small. Yes, if one uses too much chlorine neutralizer or reducing agents the chlorine demand can be high after the treatment and maybe one could get some bacterial conversion of CYA to ammonia for further chlorine demand. We do recommend people use PolyQuat to at least dampen algae growth when the FC is 0. Since most people who do the ascorbic acid treatment don't find unusually high chlorine demand, I'm not sure if it's worth a warning. Unfortunately, we don't know exactly what happened in your situation and have only speculated.

I know in my own pool when I recently did the ascorbic acid treatment I had high chlorine demand for around a week (first few days with 3 times the normal demand), but I believe that was due to my using an inferior metal sequestrant. I write about this here and here.

 

[smallpooldad]

Well who really knows what happened, so maybe the cautionary note might scare people off and then nothing would be accomplished, so I think your approach to not writing it in is better.

Thank you for all the time you spent on me it is much appreciated, and really got me thinking this thing through a lot harder. Hopefully it will never happen again. Less is more as the saying goes.

Aloha