MPS effect on FAS-DPD test

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Mitcha

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I know this is inappropriate but I;m trying to message @JoyfulNoise about an old thread about MPS...How to do it? It's about Taylor testing and Matt wrote 'To be clear - MPS shows up as excess FC on the DPD-FAS titration test (R-0870 & R-0871) and it shows up as CCs on the DPD only test (R-0001/R-0002 & R-0003). It only shows up as CC on the FAS-DPD test IF the FC level is zero'.....
But this is not the place. How to message Matt? Thank you
 
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Eliminating Interference From Potassium Monopersulfate Compounds In Chlorine Testing
Clean water.

Minimal closed-pool time.

Pool operators who use potassium monopersulfate (MPS), a chlorine-free product, have been delighted for both these reasons.

MPS oxidizes organic contaminants and maximizes sanitizer efficiency without raising the water's chlorine level.

Incorrectly referred to as “non-chlorine shock” (it is actually a non-chlorine “oxidizer”), although shocking with MPS has been a welcomed innovation, testing pool/spa water that contains MPS with a standard DPD chlorine test has not been as satisfactory.

MPS oxidizes the DPD #3 reagent (used to measure total chlorine) but not the DPD #1 and #2 reagents (used to measure free chlorine).

The endpoint of the test is a dark red, which falsely indicates the treatment has increased the chloramine level, when in reality it is the residual MPS that is being read.

To achieve accurate readings for combined chlorine, the MPS interference had to be eliminated without hindering the test's ability to distinguish between free and total chlorine.

For that reason, a "monox" test was developed for use with DPD kits that measures free and total chlorine accurately and permits calculation of the true chloramine and MPS levels.

By adding a single reagent, the R-0867 Deox Reagent, to Taylor's DPD-based chlorine test kits, pool operators who shock with MPS need no longer be concerned about inaccurate sanitizer readings.

The Monopersulfate Interference Remover kit can be purchased as an upgrade to any of Taylor's DPD-based chlorine tests in two sizes: K‑2041 (.75 oz) and K‑2042 (2 oz).

It’s also available as a stand-alone kit, the K‑1518 FAS-DPD chlorine/monopersulfate test.



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K-1518

Drop Test, Chlorine (free/combined)/Monopersulfate, FAS-DPD, 1 drop = 0.2 ppm​

 
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Mitcha said:
but I;m trying to message @JoyfulNoise
Click to expand...
Your ability to message members was disabled before your 1st post as a robo spam preventative measure. You now have the 'start conversation" icon when you click on any members name and view their profile.


Welcome to TFP !!! You have 2 of our best here already and Matt's here too. 😁
 
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Free & Combined Chlorine Test.

1. Rinse and fill sample tube to 25 mL mark with water to be tested.

2. Add 1 heaping dipper R-0870 DPD Powder and QUICKLY swirl to mix.

IMMEDIATELY add 1.0 mL R-0867 Deox Reagent and QUICKLY swirl to mix.

Sample will turn pink if free chlorine (FC) is present.

3. Add R-0871 FAS-DPD Titrating Reagent (chlorine) dropwise, swirling and counting after each drop, until color changes from pink to colorless.

Number of drops is Reading A.

IMMEDIATELY add 10 drops R-0003 DPD Reagent #3.

Swirl to mix.

WAIT 1 MINUTE.

Sample will turn pink if combined chlorine (CC) is present.

4. Add R-0871 FAS-DPD Titrating Reagent (chlorine) dropwise, swirling and counting after each drop, until color changes from pink to colorless.

Number of drops is Reading B.

5. Multiply Reading A by 0.2. Record as parts per million (ppm) free chlorine (FC).

Multiply Reading B by 0.2. Record as ppm combined chlorine (CC).
__________________________________________________________________________________________

Monopersulfate Compound Test.

1. Rinse and fill sample tube to 25 mL mark with water to be tested.

2. Add 1 heaping dipper R-0870 DPD Powder. Swirl until dissolved.

3. Add 10 drops R-0003 DPD Reagent #3. Swirl to mix. WAIT 1 MINUTE.

4. Add R-0871 FAS-DPD Titrating Reagent (chlorine) dropwise, swirling and counting after each drop, until color changes from pink to colorless.

5. Multiply drops of R-0871 FAS-DPD Titrating Reagent (chlorine) by 0.2.

Record as part per million (ppm) total oxidizer (TO).

6. To calculate parts per million (ppm) monopersulfate compound (MC) as chlorine (Cl2):

Formula: TO - (FC + CC) = MC.

NOTE: A negative value for MC may be obtained when MC is zero (0) or very low (0-0.4 ppm as chlorine).

This is caused by variables such as sample measurement, drop variation, etc.

NOTE: Refer to manufacturer's instructions for proper monopersulfate adjustment.
 

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I thank you all for that info. My tapwater has about 2ppm Chloramine, no chlorine so I now know I have to treat the CC upon a refill. I've been in contact with Taylor over my CC problem and varied results using both the colormetric and drop titration tests with the deox. I also used strip tests and Leslie's pool in store tests (a cassette with various colors and balls in it). In my few months experience, the Leslie's tests are accurate and consistent and not affected by MPS. I initially was told, as above, that deox reacts with Reagent 3. The Taylor deox can also apparently convert FC to CC. I quoted what Matt had written in a post to Taylor, and they agreed with Matt and offered some advice:
They said if you add the deox 'immediately' as the directions say, it may not report FC accurately so they may need to rewrite the directions. Here's the quote:
"A common issue when using Deox is to add the DPD powder or liquid DPD 1 & 2 to the sample and then without mixing, immediately add the deox. If you don’t mix the DPD reagents into your sample, some free chlorine is often still present when you add the deox. If you add deox to a sample that contains unreacted free chlorine it will convert it to combined chlorine. Then when you add reagent #3, you will get a false positive result for combined chlorine. To avoid this all you must do is add the DPD reagent and give the sample a quick mix. It doesn’t take much mixing for all the free chlorine to fully react with the DPD. After a quick mix, it is safe to add the deox."

That helped me some, but not completely. Taylor also wrote, after I asked about not using deox but using OTO for a TC (I know, I know that OTO is harder to read by some...)
"To answer your other questions…adding some extra powder won’t hurt results. You can measure free chlorine without using deox to remove MPS with any kit that uses liquid DPD reagents (DPD #1 & #2). Just read free chlorine within 30 seconds after mixing and you will be fine. Do not use the FAS-DPD kits when MPS is present without using deox. Your idea to use liquid DPD to measure free and then OTO to measure total chlorine should work since neither method has an interference from MPS. Personally, I prefer FAS-DPD and deox but I don’t see why your method wouldn’t also work"I

I am sorry for the delayed response, I didn't know there were any. I wonder if my CC problem was and is from the tap water and it may be di or tri and not breaking down with the superchlorination I've done. I've read that activated carbon won't remove CC so refills are already 2ppm CC. So I thought about using thiosulfate with a refill to squelch the CC then start chlorinating. Any comments on any of this is very welcomed. Thanks again.

Edited due to error saying MPS instead of deox.
 
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The chloramine in municipal water supplies is almost entirely monochloramine. It is usually created in-situ by reacting ammonia with chlorine and then injecting that into the water supply. The reaction is carefully monitored and controlled so that only monochloramine is created. Then that monochloramine stays in the water distribution system for a long time to act as a broad spectrum disinfectant. Once the water exits your hose and goes into the pool, adding chlorine (along with UV from the sun) will further oxidize the monochlormaine into chloride and nitrogen/nitrate end products. This will happen almost immediately and should not see any long term CC's. As a data point, my municipal water routinely measures about 1.6-1.8ppm CC's and 0.2-0.4ppm FC. The water in my pool never registered any CC's. I currently use a whole house water softener with granular activated charcoal that removes chlorine/chloramine from the water but that was installed many years after my pool so I can confidently say that there was no CC issue with my municipal water.
 
I use a small inflatable hot tub that is covered all the time except when people are in it usually at night or to give the chlorine some air-out time. I like to fill the tub using gas heated water from the house to save some electrical heating cost and time. I can have the tub full and up to temp in a couple hours. So in that case would the CC stay in the water and if so how to remove it? Also I read that activated carbon is great for chlorine, but will not remove chloramine. Not sure about that. Thanks for helping,
Mitch.
 
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