Quote Originally Posted by PoolDoc View Post
OK. You need to go get a cheap OTO kit.

The Taylor DPD drops only read to about 5 ppm Cl. But, at levels around 10 - 15 ppm Cl, the reading will begin to drop, and by 25 ppm, will read 0 ppm. In this same range, the phenol red will be converted to chlorophenol red -- a different indicator -- and will read high. Unlike DPD drops, OTO will NOT bleach out. If you get an OTO orange result (not shown on the test block) you need to disregard your pH reading, until your chlorine drops below 10 ppm.

There is another alternative. Diluting pool water with distilled (not: "bottled", "spring", "artesian well", etc) water will not change the pH enough to notice. Go to Walmart, get BOTH an OTO / phenol red kit (yellow/red drops) AND a gallon of distilled water. Mix pool water 50:50 with distilled water, and retest. Your DPD reading should drop by 1/2: if it goes UP, your chlorine is very high. Your pH reading should be unchanged: if it changes, trust the diluted reading more than the original reading.

The DPD-FAS test does not suffer these problems.

You need an OTO kit for quick and dirty readings, and a DPD-FAS kit for accurate ones.
OK so if I get the DPD-FAS kit (Taylor K-2006c) I should be ok?? or should I still get the OTO? Sorry for all the questions, but I want to have a trouble free pool. OH also my TA is about 160ppm.