After SLAMming.... interesting FC behaviour

[morzh]

After more than 24hrs keeping it above 20ppm (my CYA is about 45 ) for two nights my morning FC reading is above the evening one.

In short, I started about 9am Wednesday, and the last addition of chlorine was Thursday after sunset, and I measured it 2hrs after so it did have time to distribute, and was running the pump all this time non-stop.
My FC 8pm Thurs was 19.5, and 8am Fri became 21.5. CC keeps below 0.5.

Now Friday night about 7pm while still running the pump it was 15.5. I put the pump on timer now so about 7am without pump running the FC is 17ppm.
Again, the previous day pump was running non-stop all the way into the morning.

I thought it'd be dropping, not rising.




Another question is, how accurate is the test - is it +/- 0.5ppm on FC/CC?
Also, when pink solution turns totally clear, after about 30 sec it gets a very light pinkish hue which is cleared with just one drop of R0871, should I account for that or is it non-essential?

 

[Catanzaro]

Another question is, how accurate is the test - is it +/- 0.5ppm on FC/CC?
Also, when pink solution turns totally clear, after about 30 sec it gets a very light pinkish hue which is cleared with just one drop of R0871, should I account for that or is it non-essential

Yes, this is normal and you have testing error. The higher the FC, the more likely there this testing error. Read this below:


Overnight Testing Error:

Numbers ok but water has a hint of cloudiness - Page 6

Post # 114

 

[Jezza]

Your within the standard 10% +/- error rate for the FAS-DPD test.

I couldn't quite work out if you had the pump running for the am test but you need to have the pump running for at least 15 minutes before collecting a sample to test.

Yes the sample will turn pink if you let is sit for a short while but you only count the drops until clear- that is your final reading.