Hello all,

after availing myself of the wisdom on this forum for the past winter i was beginning to think i was getting the hang of the BBB system and was able to keep a pretty stable hot tub without too much fuss... relying on the results of the Taylor K2006 and using it almost exclusively to test the water. so, today - after we luxuriated for a long soak - i added 6 oz of bleach, circulated the water for 15 minutes, and then tested our 350 gal hot tub.

with a test strip it shows 3 ppm of FC - but using the Talyor K2006 at the 25 ml level it takes 15 drops (!!!) for the sample to clear = 30 ppm. repeated the tests - same results. i just bought fresh 870 & 671 reagents (and test strips), and am unable to reconcile the extreme difference in the readings.

there is no chlorine smell, the water is clear, and given the volumes of liquid bleach i'm using to sanitize, the Pool Calculator would tell me that the test strips are closer to the right answer...

any suggestions for where i am getting things wrong?

Use either a 10 or 25 mL sample. With a 44 mL sample each drop is 0.1136 ppm, so you have 1.7 ppm free chlorine.

sorry -my error - I AM using the 25 ml sample (not the 44 i wrote originally) and have edited the original post to correct it

15 drops @ 0.2 ppm/drop = 3 ppm.

Welcome to TFP!

I don't follow what you mean when you say "using the Talyor K2006 at the 44 ml level". The FAS-DPD FC/CC test in the K-2006 is designed to work with either a 10ml sample or a 25ml sample. With a 10ml sample each drop counts of 0.5 ppm of chlorine, while at the 25ml sample size each drop counts as 0.2 ppm of chlorine. If you actually used a 44ml sample each drop would count as around 0.11 ppm of chlorine.

Regardless of which way you did the test, 15 drops of titrant would be less than 15 ppm of chlorine, actually either 7.5, 3.0, or 1.7 ppm of chlorine.

Using a 25 ml sample the FC level is 3, which agrees with your strips.

By the by there is no point in doing the test with a 25 ml sample. The 10 ml sample gives you plenty of precision for pool use and saves on reagents.

oops - that was a major brain-phart!

by going to the 25 ml sample (i bought lots of 871) i was expecting to increase accuracy, but then i neglected the decimal point (although i cited - and missed - the multiplication error in the message title)

thanks so much for your prompt (!) and indulgent responses... and for not calling me the idiot i am.

Welcome to the forum. You can't possibly make a mistake that hasn't already been done...usually by us frequent posters on here!