Discrepancy between K-1000 and Chlorine drop test?

Mfinlay04

Member
Jul 8, 2021
6
Indiana
Pool Size
24000
Surface
Vinyl
Chlorine
Liquid Chlorine
So I'm new to testing, received my TF-100 two weeks ago and have been reading on this site and following the info on the packet that came with the test kit. Today was my weekly, I realized that after I ran the K-1000 OTO test, so immediately (within 5 minutes of the OTO test) grabbed some water for the drop test. On my OTO it showed that I was in the 5-10 range (which I was okay with as my CYA was 50 this morning). However, we I tested using the drop test, I only had to add 7 drops of R-0871 to return my water back to clear from the pink (R-0870) test. When testing for CC, water turned clear after 1 drop of R-0871 (which if I understand correctly is essentially zero CC).

However I was surprised that there was a large discrepancy between the two test and makes me worried using the OTO style test daily to monitor my Chlorine level. I was assume the drop test is significantly more accurate.

Anyone have similar experience or have any suggestions?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,992
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Welcome to the forum!
The OTO test is at best, an indicator that there is chlorine in the water. At what level, it is not accurate.
As you are fairly new at testing your water, you should use the FAS-DPD test every day for awhile. Even do them both so you see what shade of yellow correlates with the real FC level. Then if you need to just do the OTO, you will know what range of FC it is indicating.
I suggest you read ABC's of Pool Water Chemistry.
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
2,971
Spring Valley, NY
I think OTO is a waste of time because the range it offers are unusable. For instance is it 5 or 10. If I know the pool and know there's FC in I need a more accurate response. Haven't found any benefits with it yet.
 
  • Like
Reactions: Mfinlay04

Mfinlay04

Member
Jul 8, 2021
6
Indiana
Pool Size
24000
Surface
Vinyl
Chlorine
Liquid Chlorine
Should I be doing the FAS_-DPS test in the morning or at night? Or does it not really matter time of day?
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
2,971
Spring Valley, NY
Should I be doing the FAS_-DPS test in the morning or at night? Or does it not really matter time of day?
If you're in slam that's the only way anytime you check. If you're days away from end of slam you can then do a perfect 5ml test instead of the 10 ml with the same heaping spoon of powder, now each drop will equal 1 ppm and not half.
 
  • Like
Reactions: Mfinlay04

BenB

Gold Supporter
Jul 24, 2020
268
San Jose, CA
Pool Size
19500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
On my OTO it showed that I was in the 5-10 range
For instance is it 5 or 10

I know that you know this wireform but wanted to add for clarity for other readers and because I think OP might not. The test does not indicate "5-10". Rather, it is reading "5 if Chlorine or 10 if Bromine". Since basically nobody uses bromine that second number is meaningless yet I see a lot of new users of the test kit will post both numbers.
 
  • Like
Reactions: Mfinlay04

Mfinlay04

Member
Jul 8, 2021
6
Indiana
Pool Size
24000
Surface
Vinyl
Chlorine
Liquid Chlorine
I know that you know this wireform but wanted to add for clarity for other readers and because I think OP might not. The test does not indicate "5-10". Rather, it is reading "5 if Chlorine or 10 if Bromine". Since basically nobody uses bromine that second number is meaningless yet I see a lot of new users of the test kit will post both numbers.
I saw the kit tests both, but definitely didn't put it all together until you said that. Thanks a ton. I guess I will be going through my R-0870 faster than I had anticipated. Luckily it doesn't seem to be very expensive to replenish
 
  • Like
Reactions: BenB
Thread Status
Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.