I'm getting very different FC and CC readings - even from the same sample.

[hansn484]

Different problem, but continuing from:

Hot Tub Start Up Questions

Problem: Keeping my TA at 50 causes pH to raise to over 8+. pH was only in 7.6 range when my TA was LOW(20 ppm). I'm following the "How do I use Chlorine in my Spa" instructions for the first time(I was using frog ease prior). This is after a drain, scrub the tub, and refill with my hose...

www.troublefreepool.com

Problem: I'm getting very different FC and CC readings - even from the same sample.

My readings from most recent sample:

TA - 40
pH - 7.8

To get multiple tests I used both my TF-100 tube and the DFD 2006-k Tube for a chlorine reading using the same water sample. (Same Powder, same 0871, same 003 - just different tubes)

Both tubes came back with different FC/CC readings?

The TF-100 tube had FC - 4.5 and CC of .5
the DFD tube had FC - 1 and CC of 4

This water sample came after aerating 5 minutes so I could get a good TA/pH reading.

What should I do?

Thanks for the help.

 

[Texas Splash]

By using the same water sample and reagents, it doesn't make sense that the results would vary significantly unless perhaps the tube in one had some residue in it. Any chance the Taylor tube needed a cleaning?

 

[proavia]

Sounds like time to clean both tubes. I believe some have used isopropyl alcohol to clean the tubes.

 

[hansn484]

Cleaning the tubes and the cup I used did the trick. Thanks!

 

[dntboles]

Today when I added the first squirt of pool water into my TFT chlorine tube, it turned pink BEFORE adding any powder. Time to clean it!