aciam - Nightmare conversion from baquacil to chlorine

[waterbear]

FYI. The procedure is in this PDF file (OXYplus™ is sodium percarbonate). The dosage was 5 pounds per 10,000 gallons (so 1 pound per 2000 gallons) which is less than the dosage normally recommended for ProTeam® System Support (but the purpose is different here) -- note that this is different than I wrote to Ben earlier since I found a reference to Orenda's instructions. Also, I thought that it was added without the acid and that after the conversion then acid was added to adjust pH as needed.

Thanks Richard, I was looking for Dick Kersey's instructions and couldn't find them! I thought his dosing was half that of Proteams' but could not remember. I had lost contact with him when he moved and started his newest product line selling phosphate removes and enzymes. Remember that this is the same person who gave us the ill fated CYA reducer that does not seem to be on the market anymore. I do know that he recommended adjusting pH after conversion so he is doing it in a high pH environment but I have also personally know of conversions that were successful using the higher dosing and keeping the pH at normal levels. However, the addition of hydantions to the water (Baquacil CDX) certainly is part of the problem here. We know the effect that hydantoins have on bromine (and chlorine for that matter) and it seems that they have a similar effect to stabilize hydrogen peroxide because they are an aldehyde doner (same reason they are used as preservatives in cosmetics and shampoos). If this is the case then a drain and refill might be the only way to solve this problem unless there is some way to break down the hydantion compounds in the water.

[aciam]

Can you explain how hydantoins work on chlorine to me? Just so I understand.

I tested my hypothesis again today - this morning at 730 am numbers were TC by OTO of appromimately 5 with FC of 4 and CC 1; at noon TC by OTO was closer to 3 with FC of 3 and CC of 1 by DPD-FAS so I decided to add approximately 1/2 gal 12.5% bleach - and retested one hour later at 1 pm. ( 10k gallon above ground pool)

Here are the results: TC by OTO = approximately 5
FC 5; CC now 6


Clearly the new bleach is being routed to CC despite no one using the pool - just as I have seen over the past 2 weeks with each addition of fresh chlorine - and evidenced by little rise in the free chlorine. And also I think it seems out of the norm that my chlorine levels are so stable - for days even - without any new bleach or stabilizer at all. Something is stabilizing it and I imagine trying to maintain a pool in this state would be impossible.

I did find one other person on a different pool site who was experiencing similar problems - as you all had mentioned before - but he stopped posting and so there is no follow up. I wonder if he or reesie used the CDX system? there has got to be a group of people who used this system and are now trying to convert - so I am sure this problem has to be coming up - although if everyone only listened to the pool store, no one would be testing CC and people would be using their pools once they were clear not aware of the problem.

Now that we know about the hydantoins, does that change all of your minds about the benefit of the percarbonate and was it copper sulfate additions? This is an above ground pool - how risky is a drain refill? would it have to be fully drained or could a foot of water remain? would that leave enough hydantoin circulating in the fresh water to continue to cause problems?

I would rather pay someone to come and oversee the drain and refill to make sure it was done in the best way - (any of you want to fly up to good old massachusetts?????? ) But it sounds like there still is a risk of damaging the pool? I need to find someone good and someone who will understand why we are doing this. That will not be an easy task!

In the meantime - the good news is that I don't have to keep checking the pool that often because the chlorine is nice and stable! But I'm not sure if it is worth it to keep adding bleach - it seems like nothing is better from 2 weeks ago. I will wait to hear back from you all. aciam

[waterbear]

I still think the percarbonate is worth a shot. It is a strong oxidizer and it's worth the experiment. If it does not work you are out the price of the percarbonate, which is not that expensive. If it works you have added to our combined knowledge of pool chemistry if you are willing to do so. I have been researching online to see what I can find out about stablizaiton of peroxide by methylated hydantions and also any possible effects on biguanide (there is some indication that it may introduce additional polymerization but nothing specific that I can find so far.)

Methylated Hydantions are used to stabilize bromine and some chlorine disinfecting compounds so the sanitizer is release slowly but they have no effect on protection from UV so they are not commonly used in chlorine products for pool. If I am not mistaken the chlorinated hydantoins will test as combined chlorine but will still slowly release hypochlorous acid. (Ben, Chem Geek any info on this? What I have been able to find is really spotty and I have had to read between the lines a bit, so to speak.)
The old adage that 'bromine is forever' is true when the bromine source is from either BDCMH or DBDMH (the two most commmon bromine tabs used in pools and spas) because the DMH keeps the bromide from oxidizing to bromate and therefore to convert to chlorine you must drain and refill. When inorganic bromine is used (sodium bromide) the continual addition of chlorine and the effect of sunlight will effectively destroy the bromide ions so the cannot regenerate bromine sanitizer and the pool or spa converts back to a chlorine system again as long as more sodium bromide is not added.

If I find out anything else I will post it!

[madwil]

Been a long time since chemistry classes- but the reduction chain for hydantions looks problematic. Like waterbear said, the cheap test may work, and will give us all some data for future use.
I've been trying to reach an old buddy of mine, who works at water treatment plant (with hydantion type slow-release chlorine that waterbear mentioned) to see what they do to remove it after treating the water system- may give us a clue to pools, or may only be practical in industrial environment... problem is I've been out of touch with them for 20 years, since I joined the Navy!

[chem geek]

This MSDS shows that Baquacil CDX is 5,5-dimethylhydantoin (DMH). I can't find equilibrium constants on bromine with DMH nor chlorine with DMH. There are numerous warning-like recommendations for a DMH maximum of 200 ppm as noted in links in this post. It seems that bromine and DMH may be like chlorine and CYA where some or perhaps much of the bromine attaches to DMH. You mentioned that this did not protect bromine from sunlight, but it might help somewhat by reducing hypobromous acid concentration though not as much as CYA which has an additional UV-shielding effect. Anyway, the real question is whether there is enough chlorine that binds to DMH to report as CC. I find this unlikely since BCDMH tablets wouldn't work properly if the chlorine remained tightly bound to DMH. Though there might be an equilibrium, if it were fast enough then that would show up as FC just as it does for chlorine bound to CYA. On the other hand, DMH is the most likely candidate from what we've been looking at for the persistent CC so maybe when DMH concentrations are very high that the chlorine indeed binds to it strongly enough to measure as CC -- I really don't know. Maybe the release is slow in which case one could test for FC and wait -- if the FC continues to climb and then stops then test CC. If this time isn't too long, then this could confirm chlorine attached to DMH getting slowly released though it is already know that there is some bleed-through of CC into the FC test if one waits too long.

As for why DMH is added, it is interesting that in this link dimethylhydantoin is not listed as a stabilizer for hydrogen peroxide. It sounds more like DMH is used to help stabilize hydrogen peroxide against breakdown from sunlight. This link gives some info from the EPA on DMH where photo-degradation is noted, BUT in the atmosphere with hydroxyl radicals with a half-life of 3-1/2 days for their assumptions. This may mean that having FC in the water along with sunlight MAY help degrade DMH due to production of hydroxyl radicals, but from what we've seen in these pools it seems that this is too slow. On PDF page 38 they talk about aqueous photolysis with a half-life of 878 days (other tests described later have even longer half-lives) so clearly sunlight alone without chlorine would not be enough to degrade DMH quickly. It does biodegrade in sludge (i.e. bacterial degradation).

[aciam]

So I have read chem Geek’s last post several times to make sure I am understanding it – and wanted to present a data point from last Thursday that might shed some light on what you were thinking in terms of equilibrium of DMH and chlorine release – I have not ever done the FC CC tests on a single sample waiting 10 or 20 minutes in between tests – BUT I do have some data from multiple tests close in time after adding bleach.

Last wed I dumped a lot of bleach into the pool desperately trying to get my FC to 12-15 which was the level recommended to me on this thread – I had no more titrating reagent and was relying on “cheap” kits – the OTO for TC and DPD for FC by color matching. I could never get to 12-15 despite all the bleach I was adding – but in retrospect I now can see why. So once I got my new reagent in the mail I decided to test at multiple points after adding bleach to see what was happening to the bleach in the pool – this is when I first noted that all the bleach was combining with something to increase my CC incredibly high but only raising the FC a minimal amount.

So, last Thursday at 1pm I tested with my new reagents and got a FC =8 and CC=16

I added 1 and ½ gallons of 12.5 % bleach at 1:20pm – which should have raised the chlorine level by approximately 15 -18?? Is that right?

I tested 20 minutes later ( at 1:40) FC=11.5 ( slight inc) and CC=35 (huge increase)

I retested (a new pool sample) 20 minutes later again ( 2pm) FC=15 (now higher) and CC=25 (now lower)

After that the testing shows both numbers slowly decreasing.

I present this in case it helps to clarify your thought process – that in fact the new bleach being added seems to be primarily binding to something (the DMH presumably) right away and testing out as CC – and then slowly dissociates to increase free chlorine levels and decrease CC but only to a point. I don’t know what is governing that dissociation equilibrium. Nor is there any real consistency to the numbers – some days the CC can be high without even adding any new bleach.

I haven’t done any other testing so closely in time to adding bleach so have no other data points to present.

What I do know is that it is nearly impossible to achieve high levels of FC in this pool without pouring in huge amounts of chlorine thus causing the CC to skyrocket – and the CC levels seem to stay in the lower range when there is less free chlorine measured.

SO I guess the question is can we break down the hydantoins in any effective way to change the chemistry of the pool so it works properly. I am curious to see if madwil gets any information from his buddy at the water plant - that might give us some insight into whether anything we do could actually breakdown these substances. And whether I really need to seriously consider a drain and refill.

Then if we decide to try the percarbonate – I suppose I will need everyone’s consensus on how to do it – 1 pound or 2 per 1000gal – acid or no acid. I’m not sure I was clear on the final recommendation. Perhaps that’s because none of you are either ☺

I feel like I am back in my organic chemistry class in college – and let me tell you all – I did not like organic chemistry!!!! It is like a nightmare that has come to haunt me all these years later……..My husband just shakes his head at me when he ventures down to the basement to see me with all my bottles and reagents. It is kind of comical. If I wasn’t so upset about all of this, I’d really have to laugh at it. Maybe after this is all done I will. Thank you for all of your help. aciam

[chem geek]

According to the Orenda instructions, it's 1 pound per 2000 gallons (5 pounds per 10,000 gallons) without adding acid until you are done with the conversion.

Note this post where there might be a slow drop in CC over time.

You could do a bucket test for the percarbonate rather subjecting your entire pool to it. If it works for pool water in a bucket, it should work in the pool. You'd scale down to very small added quantities as a result. 0.016 ounces weight (somewhat less than 1/8th of a teaspoon, I think) of sodium percarbonate in 2 gallons.

[reesie]

Hi aciam,
It's reesie. Yes, I used CDX the last 1 or 2 years ( I think 2 years) and the tablets the year before just like you. I didn't realize it was going to come back to haunt me!

[chem geek]

FYI. This patent talks about using various aldehyde donors (as Evan mentioned) including DMH equilibrium compounds in water to stabilize hydrogen peroxide though that stabilization is described as preventing too much reaction from decomposing enyzmes often found in some organic matter (such as recycled paper). They don't mention stabilization with respect to sunlight. Anyway, I'm going to see if most of the conversions at TFP that went well didn't use CDX. The same should be checked here as well if possible.

[aciam]

Hi Chem geek - so the sodium percarbonate has arrived - we had a medical emergency in the family so I have had to put the pool stuff on the back burner - I am hoping to try the bucket test sometime in the next few days using 1/8th tsp of Na percarbonate in 2 gallons per your instructions but just need guidance as to what I am looking for and how long to wait before I retest the bucket water. And how I will know it has worked - or if I need to repeat the dose and retest in a certain time frame. Thanks. aciam