Thanks!...and a testing question: DPD/871 clear but K-1000 yellow

[ItCameWithTheHouse]

Firstly--thank you TFP. This forum saved the day for us and we had an easy pool maintenance year.
Now it's quite cold here in TN and we'll be closing it soon, and finally there is some confusion.

I've used the DPD/R-0870/R-0871 test daily all year because our goal TC was 7 (after a high CYA and partial refill in the spring). Over the season CYA came down further ending at a CC goal of 5. Anyway, it worked perfectly....

Now that it's cold it's only needed a small amount of bleach everyday. The last week the DPD/R-0870 test only shows clear, but the K-1000 test turns yellow. What does that mean? Essentially getting a 0 chlorine read with one method and a correct one of about 5 with the other.

Just hoping to make if through these last weeks before covering it for winter.
Thanks for the help! This is a great community.
---
15200 gallon - above ground vinyl liner

 

[Donldson]

OTO tests for Total Chlorine and the FAS-DPD test tests for Free Chlorine initially. Are you adding the R-0003 to check for Combined Chlorine after you get your reading of zero FC?

 

[ItCameWithTheHouse]

I appreciate the response.
Honestly after 6 months of a 0/clear reading, I got lazy about the R-0003 in the last few weeks.

Just tested again. FAS-DPD read 0....when I added the R-0003 it turned very faintly yellow. Not at all the normal pink.

 

[mknauss]

R-0003 is DPD Reagent #3. It should be a clear colorless liquid. If it turns yellow, it has gone bad.

How old are your reagents. The above is out of this Pool School - FAS-DPD Chlorine Test

I would contend that your FC is essentially zero. Though the following may be in play

Using the small spoon shaped end of the dipper, add one heaping dipper, or two level dippers, of R-0870 and swirl to mix. If the sample turns pink for a moment and then turns clear again, or if it turns brown, add another dipper of R-0870. If the sample remains clear the entire time, your FC level is probably zero, however it is best to verify that with an OTO chlorine test, since the FAS-DPD test is prone to the occasional false zero.

 

[ItCameWithTheHouse]

How old are your reagents. The above is out of this Pool School - FAS-DPD Chlorine Test

I would contend that your FC is essentially zero. Though the following may be in play

Thank you also for the response.

The R-0003 is from the spring when I bought the whole TFP test kit.
The FAS-DPD stuff was refilled in the summer.

After I got the levels set in the spring with the refill, I followed the TFP plan and it has been perfect all season, until this weirdness.

 

[mknauss]

Just for fun, take your water sample and bring it indoors. Let it warm to room temperature. Then test.

Cold water is not supposed to effect the FC testing much, but it is worth a try.

I will check with someone on this ---

Take care.

 

[ItCameWithTheHouse]

Just for fun, take your water sample and bring it indoors. Let it warm to room temperature. Then test.

Cold water is not supposed to effect the FC testing much, but it is worth a try.

I will check with someone on this ---

Take care.

Thanks!
That occurred to me, so I let it sit inside a couple hours. Maybe that's not long enough?

 

[mknauss]

Should be. Lets wait for some others to provide guidance.

 

[JamesW]

Cold should not have an effect.

Try adding 5 drops of R-0003 first, swirl to mix, look for color, then add R-0870, look for color again, then titrate with R-0871.

What color is your R-0870 powder?

 

[ItCameWithTheHouse]

Cold should not have an effect.

Try adding 5 drops of R-0003 first, swirl to mix, look for color, then add R-0870, look for color again, then titrate with R-0871.

What color is your R-0870 powder?

Thank you also for replying...

1.Added R-0003 first---turned a pale yellow
2.Added R-0870 powder (color looks same as normal, maybe a little dark?)---no change still pale yellow
3.Added R-0871 went back to clear in 10 drops

 

[JamesW]

Try 3 scoops of powder.

Also, test your tap water for FC and CC to see if the test is working.

 

[ItCameWithTheHouse]

Try 3 scoops of powder.

Also, test your tap water for FC and CC to see if the test is working.

Don't have enough to do that, I'll order more. Almost out and was hoping to limp through these last couple weeks until closing.

With the K-1000 test reading yellow (5--but I know it could be higher), how much should I add every day in the meantime?

 

[mknauss]

I would add the equivalent of 1 ppm FC per day. That might be too much - but will not get to shock level for awhile.

Take care.

 

[ItCameWithTheHouse]

I would add the equivalent of 1 ppm FC per day. That might be too much - but will not get to shock level for awhile.

Take care.

Will do. Thanks!

 

[JamesW]

Try testing your tap water with both tests.

 

[OTPirate]

Yes, please test your tap water per James W with both tests. The OTO should indicate the presence of CL and the dpd should give you an exact number.

 

[ItCameWithTheHouse]

Yes, please test your tap water per James W with both tests. The OTO should indicate the presence of CL and the dpd should give you an exact number.

Thank you for the response--
Tested again this morning. Tap along with some pool water that had been sitting inside overnight...

DPD still clear with both pool and tap water

OTO/L-1000 tap water was clear.
OTO/L-1000 Overnight pool water got a reading of 1--strange because it was getting a yellow/5 yesterday (tested twice a couple hours apart with same result).

Seems like the chlorine is way low and I need to get some in there.
New R-0870 powder has been ordered as well.

 

[OTPirate]

DPD still clear with both pool and tap water

OTO/L-1000 tap water was clear.
OTO/L-1000 Overnight pool water got a reading of 1--strange because it was getting a yellow/5 yesterday (tested twice a couple hours apart with same result).

EPA requires tap water to have a detectable level of chlorine in it for safety reasons. If your OTO indicated the presence of CL in your pool, it is obviously working, and it will indicate the presence of CL in your tap water. You can also try the OTO test and DPD test with VERY DILUTED bleach.

 

[JamesW]

Tap water will usually have low fc but some cc. Most chlorine in tap water will be cc.

 

[duraleigh]

Aside from apparently only one OTO test. you have tested NO chlorine (or negligible) each time, right?

Put enough chlorine in your pool to get to 4 ppm (use PoolMath) and I think you will find both your FAS/DPD and OTO test will work.

I think you likely had some form of testing error on that one test. Chalk it up to "one of those things" and move on.