Testing at >20ppm SLAM free chlorine?

[Degasiado]

Hi,

I am experiencing some slight algae and have initiated the SLAM process. My CYA is 60 so SLAM is done with FC of 24as per the chart; however the taylor k2006 kit says FC testing with fas-dpd is accurate up to 20ppm. How should I proceed in this case in particular when doing an overnight loss test? If this is not accurate i will not be able to confirm if i pass the <1ppm loss, right?

I would appreciate any advise.
Thanks!

 

[mknauss]

Using a 10 ml sample of pool water, the FAS-DPD test is accurate to 50 ppm FC.

 

[Degasiado]

Using a 10 ml sample of pool water, the FAS-DPD test is accurate to 50 ppm FC.

That’s odd, the chart in the kit states a range limitation of 0-20ppm free and combined chlorine fas-dpd

 

[Newdude]

That’s odd, the chart in the kit states a range limitation of 0-20ppm free and combined chlorine fas-dpd

The industry doesn't believe in the FC/CYA relationship and treats each as independent of the other. So to them, you have no business being above a 5 FC. 'Shocking' is a dump and pray tactic that doesnt resly on testing so they only cared to certify the kit to 20. The same Taylor reagents were tested here and proven to be accurate to 50 like Marty said above. Ironically, they were probably better than that too, but good luck making 100+ perfect drops to prove it.

 

[Degasiado]

The industry doesn't believe in the FC/CYA relationship and treats each as independent of the other. So to them, you have no business being above a 5 FC. 'Shocking' is a dump and pray tactic that doesnt resly on testing so they only cared to certify the kit to 20. The same Taylor reagents were tested here and proven to be accurate to 50 like Marty said above. Ironically, they were probably better than that too, but good luck making 100+ perfect drops to prove it.

Noted, thanks! Will proceed then. I have noticed that doing the test back to back results in slight deviations in measurement, likely due to not having the exact amount of pool water in the tube or drops (about 50) not being all the same. Will use the average measurement work?

 

[mknauss]

During a SLAM, being off 1 or 2 ppm FC either way is not a big deal.

If for your OCLT you are not getting consistent results, be sure to clean the vial with rubbing alchohol, and, you can let the FC drift down to 20% or so of CYA level and do the OCLT there.

 

[Newdude]

Will use the average measurement work?

Thats a good way to make up the human error, but as long as you are in target range, the only # that really matters is the 8, not the 8.5 so its really not neccessary. If you are dancing the line at minimum, then yes, .5 could make all the difference in the world.

Being a few drops off with the 10ml wont matter either. Say you miss 2 whole drops of the 50 (taking your word here). Thats 4% and only changes the 8 FC reading by .3. You are still well above minimum. If you are down to 3 FC, and the goofed test is off by .2, it is far more important that you add 5FC. (Or whatevs to get back to target range).

Anywho, just take your time and have the gentlest of squeezes so that gravity makes the perfect repeatable drops. I promise you, if you rush, you will never know you saves 17 seconds. This way your OCLT will be dead on. The OCLT also has human error built into the acceptable 1 FC loss, just in case.

 

[JoeSelf]

Hold the bottle upright and let the drops fall off the tip. Don't squeeze them out.