Given my CYA levels, my ideal FC is 4ppm. Although this is ideal for my pool, it isn't ideal for my basic test kit which only goes to 5ppm. Instead of using up all my FAS/DPD test contents from my TF-100, is there a reliable way to manipulate the OTO test? I was thinking something like this: if 3 drops gives me a 5ppm reading, can I multiply that result by the ratio of drops I used to get the proper chlorine reading? IE 3 drops means 40% of the OTO that was supposed to be added, wasn't. So add that 40% to the 5ppm result (5x1.40) for the actual chlorine reading (7ppm).
Is this reliable? Or even correct? I'm no math whiz... lol

Nope.

I already asked that. Just searched for my post, but can't find it. Apparently, the reagent is an indicator rather than something that reacts. Wish I could find that post.....

I rely on the FAS-DPD test, but since I have the OTO, I often use it just to see if I'm getting any better at reading it. And I'm not. I've been certain 4.2 was higher than 5 and thought 6.8 was approximately 4 just this morning.

To conserve the TF100 reagents, use a 10 ml sample. Also, one scoop of powder should be enough. My rule of thumb is that there should be one or two crystals left undissolved before adding any R-0871. If it's bright pink and you have some extra, it's enough. They will dissolve when you start adding reagent. Don't know why, but that has worked well for me.

****, too bad. Thanks for the clarification though. As for conserving reagents, aren't 10ml samples the norm for the FAS/DPD test? That's what Ive always done, which I think is what the TF-100 told me to do...

Yes 10ml is the normal but you can use 25ml samples and multiply by .2

PLEASE stop conserving the chemistry in the TF-100. I have two children in college

Okay, now that I got that out of the way ....

Probably the best way to save that expensive FAS/DPD chemistry is to perform the test less often. That almost always comes with familiarity of your pool.

Most folks start off testing very frequently but, as they learn the chlorine demand of their individual pools, many find they can dose on a regular basis and get predictable results.

For my pool, I use the OTO daily (pretty much) and just look for it to have roughly the same intensity of yellow. After seven years of testing, I am able to do the FAS/DPD test only once weekly and I find I seldom have to adjust much.

There is no substitute for experience, though. My daughter had a pool party yesterday, and, without testing, I added a dose of 1 gallon of 12%. That gave me an extra 2ppm of FC prior to the bather load and the pool came through as if the extra bather load was never there.

I'm not tooting a personal horn but just saying that, with time, you will learn the in's and out's of your pool and will develop ways of managing your water without quite so much testing.......much to my disappointment.

Keeping a good, detailed log book of conditions, testing and results is invaluable as well. That to include rain, temps, evaporation, water additions...............(and the occassional mishap).

One way to approach things is to use the FAS-DPD test about once a week to figure out exactly how much chlorine you need to add each day. Then you use the simpler OTO test daily as a simple chlorine/no chlorine test just to make sure that nothing has gone drastically wrong.

Well, I like testing and knowing exactly what my FC is...and I like seeing how close I get with educated, and experienced guess addtions.

I'll justify it by knowing I'm giving to a good cause.

Brushpup,

I have asked that you be moved into the top ten all-time favorite posters...(well, my top ten anyway )

How about both lists, or.... You could run a BOGO special just for me sometime.