Question about using titration method for testing cl levels

[Armytiger]

I recently bought Taylor's FAS-DPD test kit and I'm not sure if I'm calculating cl levels correctly.

Over the past week, I have been getting "permanent color" change after adding one maybe two drops R-0871, and have assumed that my cl levels were still low despite being able to slightly smell cl while in the pool and having some eye irritation while swiming.

When I tested my pool water this evening, I saw a "permanet change" after the first drop, AGAIN. However, tonight I was distracted and noticed that after a couple of minutes of allowing the 10 mL vial to stand alone that the solution changed back to pink.

I added a couple more drops, shook solution, and again "permanent change". Let it rest a couple of minutes and noticed it changed back. I let the sample rest for over an hour and it became a dark pink instead of a light pink as it has always been.

How long am I supposed to wait for a color change back to pink before making the determination that the change is permanent?

[PoolDoc]

I don't fully understand it, but DPD does react to some chloramines given time. I can't really tell you more than that.

HOWEVER, that might not be your issue. If you don't rinse your sample tube out well AFTER each test, you can get similar, but bogus, results

Still, in your case, I think it's chloramines or CC, since you are smelling the chlorine. That will happen if you let your chlorine get low. I think the important question here is not the one you asked, but this one: "Why are chlorine levels in my pool so low?"

That's the question you need to answer.

[waterbear]

According to taylor you read the test immediately after the change. Also, do not shake the vial (on any of the titration tests, the only test that should be shaken is the CYA test) you want to swirl it.
A bit more information, are you referring to the first part of the test for FC or the second part of the test for CC?
It is very possible to have low FC but high CC and if you are not doing both titrations (titrating and then adding R-0003 and titrating again) you would not know this. You are doing both titrations, right?

Taylor Technologies has a page of videos (http://www.taylortechnologies.com/products_choose_slideshow.asp) that show how to do the tests properly. Click on POOL/SPA on the upper left then scroll down and click on To Test (Free and Combined) Chlorine using FAS-DPD [updated 3/5/10] for a video on how to do the test.

[Armytiger]

Ben . . . my cl levels were low b/c I had to treat for metals. (see link http://www.poolforum.com/pf2/showthread.php?11684-Metals-or-Algea-Please-Help). I was slowly raising cl by adding a quart a day until my test kit arrived, whcih finally happeneded last monday. I have been trying, unsucessfully, to raise my cl levels by adding bleach and trichlor tabs via the inline chlorinator. However, I have not seen any rise in my FC or CC after adding doses ranging from 6-9 ppm of bleach. (I had been reluctant to add shock level doses to my pool based on the mbar's write-up concerning metal treatment until now) For example last night I added just over 4 gallons of bleach which should be a does of 11 ppm for my (25,550 gallon pool). When I tested the water this evening I still had basically undetectable cl levels.

Test results:

FC=.4
CC=.2
pH=7.1
TA= 90
CYA=60

Based on what I have read about chloramines it seems that my next step is to shock the pool. Using the "best guess chart" my dose should range somewhere between 20 and 75 ppm of cl. This is a pretty wide range. What is your reccomendation for raising my cl levels?

Thanks

[aylad]

For a CYA of 60, then 20 ppm should be high enough for a shock. Raise the chlorine slowly, watching for any visible sign of staining.

Janet

[Armytiger]

Please disregard the test message. I had previously posted a message that somehow was lost in the submittal process.

To make a long story short I have shocked my pool twice over the past week. Once with a 20 ppm dose (8 gallons of 6% hypo) and yesterday I added an additional 13 gallons of 6% hypo.

I tested my water today and here are the results:

FC=.2
CC=.2
pH=7.6
TA= 90
CYA=60

Please let me know what I should do next to get my cl levels up. I am adding bleach to pool by pouring it directly into the skimmer. My return inlets go through a cascading fountain (is the bleach evaporating).

Is it safe for me to swim with cl levels so low knowing that I have added over 20 gallons of bleach over the past week?

[aylad]

I would not swim with chlorine levels that low. With a CYA of 65 (which by the way is high enough--I would take the tabs out of the chlorinator and switch to plain bleach if this were my pool--the pucks are going to continue to raise your CYA, which in turn raises your chlorine level to maintain), you shouldn't have chlorine levels of less than 5 ppm...ever. If you are losing chlorine that quickly, then there's something consuming the chlorine in the water. In order to kill it off, you're going to need to get up to that 20 ppm dose and hold it there by testing and adding more chlorine as needed until the levels start to hold.

Janet