Why is my combined chlorine gradually increasing?

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MPurcell said:
I added MPS. I couldn't find a definitive answer about how much to use in my situation, so I settled on a first dose of 1 oz by weight for 230 gallons. Before the first addition my chemistry numbers were:

FC 7.5
CC 1.5
pH 8.0

I ran the air for a few minutes while I added the MPS and then let the pump circulate for an hour, and my chemistry numbers were:

FC 7.5
CC 1.5
pH 7.6

So I then ran the air for about 15 minutes after adding a second ounce of MPS, and then let the pump circulate for the rest of an hour, and my chemistry numbers were:

FC 10.0
CC 2.0
pH 7.5

So clearly, the MPS registers as FC as well as perhaps CC. I'm not sure how to interpret the numbers. But I have evidently put in enough MPS to still have an MPS residual in the water after an hour, so I guess we'll see how the numbers react in the following days.

@Arobbert, how much MPS did you use as a weekly shock to reduce CC's? Or was it daily?
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I corrected my follow-on post as it was incorrect. You might consider purchasing this test kit - Drop Test, Chlorine (free/combined)/Monopersulfate, FAS-DPD, 1 drop = 0.2 ppm or simply get the deoxidizer reagent - Reagent Pack,Monopersulfate Interference Remover (for 2000 Series kits w/ .75oz reagents K-1515-A) if you plan to use MPS as part of your tub.

MPS will definitely show up as CCs in your testing.
 
Matt, I read the article by Taylor on interference. First of all, the statement is that "The key concept to note here is that monopersulfate products will NOT remove existing combined chlorine but only prevents the formation of new combined chlorine." This seems to indicate that I will not be able to reduce the combined chlorine much except by partial or complete water replacement. The article also states that MPS only shows up in the FAS-DPD titration test as combined chlorine. However, evidence from my own testing indicates that the second 1 ounce dose of MPS raised the free chlorine level from 7.5 ppm to 10.0 ppm in a one hour time period when there were no other variables. We soaked for 22 minutes last night and I added 2 oz of 8.25% bleach after the soak, which is slightly less than the 2-1/4 or 2-1/2 oz I usually add. This morning the readings were FC 9.0 CC 1.5. I would also note that in my various reading, someone suggested that Taylor is in Dupont's pocket with that article, which seems to promote MPS. I guess the only thing to do at this point is to observe over the next week or two and see what happens with regular chlorine dosing.

I also read the thread started by chem geek about MPS use recommendations by Dupont. I seriously don't think I would dose 1 oz by weight every day after soaking! Even if that number is high, is seems to me that a smaller regular dose of MPS would both be too expensive and make it difficult to get reliable test results, not to mention the problem with pH.
 
MPurcell said:
Matt, I read the article by Taylor on interference. First of all, the statement is that "The key concept to note here is that monopersulfate products will NOT remove existing combined chlorine but only prevents the formation of new combined chlorine." This seems to indicate that I will not be able to reduce the combined chlorine much except by partial or complete water replacement. The article also states that MPS only shows up in the FAS-DPD titration test as combined chlorine. However, evidence from my own testing indicates that the second 1 ounce dose of MPS raised the free chlorine level from 7.5 ppm to 10.0 ppm in a one hour time period when there were no other variables. We soaked for 22 minutes last night and I added 2 oz of 8.25% bleach after the soak, which is slightly less than the 2-1/4 or 2-1/2 oz I usually add. This morning the readings were FC 9.0 CC 1.5. I would also note that in my various reading, someone suggested that Taylor is in Dupont's pocket with that article, which seems to promote MPS. I guess the only thing to do at this point is to observe over the next week or two and see what happens with regular chlorine dosing.

I also read the thread started by chem geek about MPS use recommendations by Dupont. I seriously don't think I would dose 1 oz by weight every day after soaking! Even if that number is high, is seems to me that a smaller regular dose of MPS would both be too expensive and make it difficult to get reliable test results, not to mention the problem with pH.
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I’d have to look further into the chloramine chemistry but I’m not sure I agree with MPS not destroying organic chloramines. I’ll see what I can dig up.

It is possible for the MPS to register as FC. The ferrous ammonium sulfate (FAS reagent R-0871) drops are a reducing agent so they can react with the oxidizing MPS and thus cause an apparent increase in the number of drops used. I think the reaction might be slow depending on concentration of MPS. So it is possible to see interferences on both sides. This is why getting the deoxidizer reagent to remove the interference is helpful.

Yes, DuPont obviously has a financial interest in users using the maximum dose possible. I would only use enough MPS to get the desired result and not anymore than that. Small, continuous dosing is certainly a possibility BUT, if that’s how you do it, I would definitely get the interference removal reagent.
 
MPurcell said:
Matt, I read the article by Taylor on interference. First of all, the statement is that "The key concept to note here is that monopersulfate products will NOT remove existing combined chlorine but only prevents the formation of new combined chlorine." This seems to indicate that I will not be able to reduce the combined chlorine much except by partial or complete water replacement. The article also states that MPS only shows up in the FAS-DPD titration test as combined chlorine. However, evidence from my own testing indicates that the second 1 ounce dose of MPS raised the free chlorine level from 7.5 ppm to 10.0 ppm in a one hour time period when there were no other variables. We soaked for 22 minutes last night and I added 2 oz of 8.25% bleach after the soak, which is slightly less than the 2-1/4 or 2-1/2 oz I usually add. This morning the readings were FC 9.0 CC 1.5. I would also note that in my various reading, someone suggested that Taylor is in Dupont's pocket with that article, which seems to promote MPS. I guess the only thing to do at this point is to observe over the next week or two and see what happens with regular chlorine dosing.

I also read the thread started by chem geek about MPS use recommendations by Dupont. I seriously don't think I would dose 1 oz by weight every day after soaking! Even if that number is high, is seems to me that a smaller regular dose of MPS would both be too expensive and make it difficult to get reliable test results, not to mention the problem with pH.
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My experience supports the idea that MPS will not affect existing CC. I tried and found no noticeable change. Maybe I didn't use enough.
 
There is some limited evidence (hidden behind a DuPont firewall) that Oxone (DuPont's trademark name for MPS) will oxidize monochloramine and simple organic chloramines but not more complex chloramines than that. It will also oxidize ammonia (but so does chlorine).

So, the best approach for using it is as a preventative maintenance chemical as it may not solve any problems with persistent CC levels. A UV system would be better for that but that's an expensive retrofit in most cases. If you do choose to regularly use MPS, I would highly recommend that you get the MPS interference reagent so that you can properly dose and measure your MPS levels and then replace the tub water on a very regular basis (2-3 month interval) so that the build up of sulphates in the water does not damage heater elements. Chloride and sulfate ions in water increase certain types of corrosion (crevice and pitting corrosion) in cheaper Incoloy heaters. Titanium heaters are better suited for use in water environments that contain chlorides and sulfates.
 
Matt, thanks for the additional research. I'll report back in a week or two whether there was any long term reduction in CC from my one treatment.

So I guess the question is whether to try to use MPS as a preventative, or to follow Arobbert's idea of just living with the combined chlorine as long as the water is clear and there is no chlorine smell. By my experience so far, it looks like it will take around 2 months from initial fill for the CC's to build up to a solid 2 ppm, and then a partial water exchange could reduce CC and extend the time till a drain and refill. With the possible additional wear and tear on the heater element and other internal parts, and the additional work of testing and maintaining the water chemistry, it hardly seems worth it. This is a relatively inexpensive tub, under $500.00, so I doubt the heater is titanium, and it would be important to preserve it's life for as long as possible.

I also may start leaving the cover off for 30 min to an hour after dosing the water with bleach each evening to see if that helps.

For anyone interested in trying MPS as a preventative, I did find an inexpensive source for the Deox and measuring dropper at Amato Industries. Currently R-0867-C for $9.45, 4030 pipet with dropper cap $1.89, plus shipping.
 
MPurcell said:
Matt, thanks for the additional research. I'll report back in a week or two whether there was any long term reduction in CC from my one treatment.

So I guess the question is whether to try to use MPS as a preventative, or to follow Arobbert's idea of just living with the combined chlorine as long as the water is clear and there is no chlorine smell. By my experience so far, it looks like it will take around 2 months from initial fill for the CC's to build up to a solid 2 ppm, and then a partial water exchange could reduce CC and extend the time till a drain and refill. With the possible additional wear and tear on the heater element and other internal parts, and the additional work of testing and maintaining the water chemistry, it hardly seems worth it. This is a relatively inexpensive tub, under $500.00, so I doubt the heater is titanium, and it would be important to preserve it's life for as long as possible.

I also may start leaving the cover off for 30 min to an hour after dosing the water with bleach each evening to see if that helps.

For anyone interested in trying MPS as a preventative, I did find an inexpensive source for the Deox and measuring dropper at Amato Industries. Currently R-0867-C for $9.45, 4030 pipet with dropper cap $1.89, plus shipping.
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After reading Matt's post I agree with your conclusions MPurcell. Anyone want to buy a bunch of MPS? Water is relatively cheap for me in MI so a 3 month refill cycle is a reasonable solution. I guess at the end of the day a CC level of 2 is not a big deal if it remains in check.
 
Can someone give me some insight on how to use the R-0867-C reagent to eliminate MPS from the test numbers?
I have the k-2006 and the R-0867 reagent. When using MPS I see a rise in FC and CC as well. I know they say only CC will be interfered with but I see it in FC as well.
Will the r-0867 allow me to get accurate FC reading as that is what I really care about. The CC reading is not as critical on a daily basis.
How are others testing in this scenario?
 
SpeedStar said:
Can someone give me some insight on how to use the R-0867-C reagent to eliminate MPS from the test numbers?
I have the k-2006 and the R-0867 reagent. When using MPS I see a rise in FC and CC as well. I know they say only CC will be interfered with but I see it in FC as well.
Will the r-0867 allow me to get accurate FC reading as that is what I really care about. The CC reading is not as critical on a daily basis.
How are others testing in this scenario?
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See here - https://www.taylortechnologies.com/en/Image/GetDocument/1275
 

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MPurcell said:
Matt, thanks for the additional research. I'll report back in a week or two whether there was any long term reduction in CC from my one treatment.
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I never did report back on this. I found that adding MPS made little discernable difference in the combined chlorine. According to my records, I had just added 20 gallons of water which reduced the CC to 1.5 the day before adding the MPS. The combined chlorine remained at 1.5 for about three weeks after adding the MPS and was at 2.0 when I finally refilled the tub on 11/4/17.

So I guess the question is whether to try to use MPS as a preventative, or to follow Arobbert's idea of just living with the combined chlorine as long as the water is clear and there is no chlorine smell. By my experience so far, it looks like it will take around 2 months from initial fill for the CC's to build up to a solid 2 ppm, and then a partial water exchange could reduce CC and extend the time till a drain and refill. With the possible additional wear and tear on the heater element and other internal parts, and the additional work of testing and maintaining the water chemistry, it hardly seems worth it. This is a relatively inexpensive tub, under $500.00, so I doubt the heater is titanium, and it would be important to preserve it's life for as long as possible.

I also may start leaving the cover off for 30 min to an hour after dosing the water with bleach each evening to see if that helps.
Click to expand...

I left the lid off for at least 30 minutes after soaking and adding chlorine, pretty consistently during the last fill cycle, 11/4/17 to 2/20/18. This may have slowed the development of combined chlorine somewhat, but not enough to be conclusive. According to my notes, CC first tested 0.5 on 11/21, 1.0 on 11/28, 1.5 on 12/18, and 2.0 on 1/12/18. CC was still 2.0 before refilling on 2/20.

For anyone interested in trying MPS as a preventative, I did find an inexpensive source for the Deox and measuring dropper at Amato Industries. Currently R-0867-C for $9.45, 4030 pipet with dropper cap $1.89, plus shipping.
Click to expand...
 
I found the same results shocking with MPS. I also found it affected the PH which created additional work. There was no significant effect on CC levels compared to chlorine. As mentioned you have to use it daily from the start to have an effect on CC's. MPS doesn't appear to be of much use if you're using chlorine.

I've been using a peristaltic pump to maintain a constant chlorine level between .5 and 1 and dosing to about 5 ppm per bather after each use. This has been working great. I can skip days without use or testing and the water is trouble free.
 
I did a very quick search. There's always the super cheap chinese products: https://www.amazon.com/Waterproof-Sterilizer-Aquarium-Submersible-Sterilization/dp/B01LXYK6PO

WARNING: If you decide to get that UV light, do NOT under ANY circumstances put any part of your body into the water when the light is in the water and plugged in. I'm not endorsing any brand. Caveat emptor.

It probably won't last long either, but for an experiment the price is right. May do it myself when my CC's end up getting high and not going away. My setup is just like the OP's.
 
Arobbert said:
I've been using a peristaltic pump to maintain a constant chlorine level between .5 and 1 and dosing to about 5 ppm per bather after each use. This has been working great. I can skip days without use or testing and the water is trouble free.
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What pump are you using? I'd like to have a pump but the stenner ones are expensive.
 
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