FAS DPD and OTO chlorine rise after non-chlorine shock

[mknauss]

Jandy Aqualink RS - Further Reading

www.troublefreepool.com

Show us a picture of your Return side plumbing. Where the Spa and Pool water returns to the pool.

 

[jmcmd1980]

Jandy Aqualink RS - Further Reading

www.troublefreepool.com

Show us a picture of your Return side plumbing. Where the Spa and Pool water returns to the pool.

Here it is, thanks. Jim

 

[jmcmd1980]

Yes, you're interpreting it wrong.

The important thing to know is that KMPS reacts with R-0871 and also with R-0003. When people say that KMPS only interferes with the CC measurement, they're talking about the color-matching DPD test, not the FAS-DPD titration ("drop") test.

In the DPD test, you first measure FC by adding reagents and comparing colors -- this part isn't affected by KMPS -- and then you measure total chlorine by adding R-0003 to the solution and comparing colors again. KMPS in the water will react with the R-0003, producing a falsely high measurement of total chorine. Since total chlorine is FC + CC, and the FC measurement was accurate, CC falsely appears higher than it really is.

In the FAS-DPD drop test, KMPS reacts with the R-0871 FAS drops, so in that test it's the FC measurement that is falsely high. By the time R-0003 is added to the solution to measure CC, all of the KMPS has already reacted, leaving none to affect the CC measurement. So in the FAS-DPD test, KMPS affects the FC measurement but not the CC measurement.

KMPS will dissipate in a few days. But if you anticipate that you'll be using KMPS regularly, you may want to purchase Taylor's K-. kit, which eliminates KMPS interference from the chlorine tests. A link to the kit is in my signature.

Here it is, thanks. Jim

Jandy Aqualink RS - Further Reading

www.troublefreepool.com

Show us a picture of your Return side plumbing. Where the Spa and Pool water returns to the pool.

Here is the spa

 

[mknauss]

So to automate Spillover, you would change the Dipswitch and change out whatever is on Aux3. Then you can close the manual valve on your return to the Spa Return. Then set up a schedule to run the Spillover twice a day for 30 minutes or so, at an elevated rpm. You will also just be able to select Spillover in your app whenever you want it to run for aesthetics, at the higher rpm to make it work. Your overall Pool mode rpm could then be lower.

 

[jmcmd1980]

I will give it a try. The spa only fills from the bottom and overflows the top until I switch to spa mode, then the jets activate. While the spa is off overflow, spa water would not be exchanged, but would during the automation times, if I understand correctly. Thanks, again! Jim

 

[Bperry]

Last weekend, I had a heavy bather load so I used 2 bags of Leslie's Fresh N Clear non-chlorine shock. I have a SWG, pool installer set to 85% and left it at that when they abandoned me. My pool is about 5-6 weeks post fill.

Today on testing, Free and combined chlorine by FAS-DPD is 9.2, had been running just under 5 prior. I did the simple OTO test also and sample turned dark yellow.

Is this an artifact of the oxidizer in the Fresh N Clear. I found one forum entry alluding to this. Do I need to do anything about this? Reduce SWG or leave it alone and let chlorine return to normal levels?

Thanks as always, Jim

What’s your CYA level? If it last high, your chlorine level may not actually be high.

 

[jmcmd1980]

Last test 60-70

 

[Bperry]

Last test 60-70

At that CYA level the normal range is 5-10ppm so it’s perfectly fine.

 

[jmcmd1980]

Yes, you're interpreting it wrong.

The important thing to know is that KMPS reacts with R-0871 and also with R-0003. When people say that KMPS only interferes with the CC measurement, they're talking about the color-matching DPD test, not the FAS-DPD titration ("drop") test.

In the DPD test, you first measure FC by adding reagents and comparing colors -- this part isn't affected by KMPS -- and then you measure total chlorine by adding R-0003 to the solution and comparing colors again. KMPS in the water will react with the R-0003, producing a falsely high measurement of total chorine. Since total chlorine is FC + CC, and the FC measurement was accurate, CC falsely appears higher than it really is.

In the FAS-DPD drop test, KMPS reacts with the R-0871 FAS drops, so in that test it's the FC measurement that is falsely high. By the time R-0003 is added to the solution to measure CC, all of the KMPS has already reacted, leaving none to affect the CC measurement. So in the FAS-DPD test, KMPS affects the FC measurement but not the CC measurement.

KMPS will dissipate in a few days. But if you anticipate that you'll be using KMPS regularly, you may want to purchase Taylor's K-2042 kit, which eliminates KMPS interference from the chlorine tests. A link to the kit is in my signature.

I added the Leslies fresh and clear on 7/17/23. Today, 7/21/23, my FC is 7.5, CC 0. Can I assume that the oxidizer is gone and it’s effect on free chlorine test is also gone?

Just an aside, if you use a 10 mill sample, is one scoop of the powder reagent adequate?

Thanks again

Jim.

 

[BDY]

One heaping scoop … you want it turning a decimate pink color and maybe a few grains undissolved at bottom is good too…

Don’t need two scoops….

 

[jmcmd1980]

One heaping scoop … you want it turning a decimate pink color and maybe a few grains undissolved at bottom is good too…

Thanks!

Don’t need two scoops….