How am I getting different chlorine readings?

[JulieS1007]

We've had a maintenance company cleaning the pool since last February. I wasn't totally satisfied with them, but it was a DISASTER of a year last year (literally...) and cleaning the pool was the FURTHEST thing on my mind. The biggest complaint is that even though they come every single week, we are still having algae. I'm ready to find a new pool cleaner and did a complete TF-100 testing today to see exactly where the levels are so I can go over them with the companies I plan to get quotes from. Ugh. Levels are just all over the place. I'll post everything at the end, but what I don't understand is how I got 2 different chlorine results from the same water?? The basic test from the K-1000 showed the chlorine to be at least 5. It was super bright yellow. So I did the chlorine drop test to get a more accurate number. But that test gave me a reading of only 3.5! How is that possible?? It didn't show any CCs either so I'm super confused by that. Maybe I didn't have enough powder in it?? Was my "heaping scoop" not heaping enough??

Full results as follows:
FC: 5 or 3.5 ??
pH: 7.8
TA: 160
CH: 260
CYA:90

 

[geko29]

Can't answer most of your questions, but it definitely isn't the scoop not being heaping enough. I have no trouble at all getting readings of 16+ out of a well-rounded scoop of the DPD powder when doing a SLAM

 

[Donldson]

The FAS-DPD test is accurate and reliable. The OTO test really isn't, the difference between what shade 3.5 would be and 5 is so minuscule there is not much chance you could tell the difference.

Ignore the OTO test, trust the FAS-DPD one.

 

[JulieS1007]

The FAS-DPD test is accurate and reliable. The OTO test really isn't, the difference between what shade 3.5 would be and 5 is so minuscule there is not much chance you could tell the difference.

Ignore the OTO test, trust the FAS-DPD one.

Ok, thanks! Either way, it's way too low for the CYA level. I even told them that when I was maintaining the pool myself, it did best keeping the chlorine closer to 5 (with a lower CYA). They wouldn't even listen and said they maintain pools between 1-3, regardless. Ugh...I wish I would've had the mental capacity to shop around for someone else before this point.

 

[tim5055]

I'm sorry but you will never find a company that will maintain a pool to TFP standards, for several reasons....

1. They will only be there once, maybe twice a week

2. They train their folks to treat all pools the same (maintain pools between 1-3, regardless)

3. They really don't care If there is a problem, that's an extra cost to fix the problem.

Just take care of it yourself....