Middle of Slam - First time testing FAS-DPD


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
I'm not 100% with the rounding up crowd for cya just yet. I'm still struggling with an old school tfp mindset tho. I think you can tell the difference between 55 and 60 in the tube, and it will allow you to SLAM at 2ppm less fc.
The scale between lines is logarithmic, not linear. Halfway between lines is not 5. You cant judge what it is. So you then cannot take that wrong reading and interpolate values from the FC/CYA Chart.

Garbage in, garbage out.

Trying to shortcut the SLAM Process is what leads many to frustration.


Jun 3, 2017
I definitely can see the bottom of the pool with nothing on the bottom or walls. The pool is crystal clear. Clear water on the backwash and rinse. Vacuum doesn't have anything in it either. When do I start testing the pH? When will that read correctly?


Gold Supporter
LifeTime Supporter
Jul 16, 2010
Portland, Oregon
OK, I get it. I do realize shortcuts don't work. I am still struggling with old TFP mindset. Doh! It is better to assume 60.

Better yet to vacuum to waste today and replace some water to get it down to 50. Shrug... She's been overdosing to 28ppm FC and it's working nicely.


Silver Supporter
Jun 20, 2018
Annapolis, MD
I see you have stairs in your pool. Pull those out and check them over well for Algae, wash them well with chlorine/bleach. Algae hides in stairs and ladders, and in light niches.


Well-known member
Aug 8, 2018
Plainfield, IL
Since your SLAM FC target is so high, switch to 5 ml test sample, one spoon of powder and then 1 drop = 1 ppm
You will loose some precision but for SLAM it's good enough. Otherwise you will burn thru your drops really fast.