View Full Version : Total Alkalinity Test

04-02-2006, 12:56 PM
Here's the deal. We just had our pool installed (specifics are in my signature). I've been testing the water almost daily (only skipped a day or two) trying to get everything balanced. I pre-ordered Ben's test kit, but in the mean time I am using the test kit that the contractor gave us with the pool. It tests chlorine/bromine (.5-5), pH (6.8-8.2), acid demand, and total alkalinity. I put 9 pounds of CYA in the pool a couple of weeks ago and don't have a way to test to see what the level is yet. I just discovered (after closer examination of the label) that the sticks they gave me in my "start up kit" are tri-chlor...I know I should be surprised at that. I've only used 4 sticks so far (they are only about halfway disolved after a week), so hopefully that won't screw up my CYA too much. According to the Bleach Calculator I got from whoever it is on this site (thank you!), after adding 9 pounds of CYA I should be somewhere between 40 -50 ppm after starting from zero for my size pool. I'm going to take a sample down to the local Leslie's store this week and see what they say the level is since they say "free water testing" in their add in the phone book. I would take the sample to the contractor that built the pool, but they're 30 miles away. Anyway, back on topic...I've been using baking soda to raise the total alkalinity...adding 4 pounds at a time and waiting a day or two to add the next box. It's starting to get difficult for me to tell what the actual alk reading is. When I add and swirl the 3rd set of drops after about 3 drops (30 ppm) the sample will turn from green to red for a split second during the swirling then turns back to green. (I swirl the test vial about 5 or 6 complete circles.) The next drop (40 ppm) turns red for a split second during the swirling and then turns clear. The next drop (50 ppm) will finally turn red and stay red. Which reading is the one I use? 30, 40 or 50? The instructions that came with the kit say "After each drop, count and swirth to mix until color changes from green to red."

I just tested this morning, and my Cl was around 1-2 and the pH was 7.2-7.5. (It's so darn hard to tell with this test vial...I hate it. I hope Ben's is easier to read.)

04-02-2006, 01:13 PM
The last number is the correct one. When using a test such as this, the reading when the color changes to the desired color and stays there is the number to use.

04-02-2006, 02:43 PM
Thank you. That's what I assumed (which is why I kept adding drops), but wanted to be sure. We all know what usually happens when you "assume".:rolleyes:

04-02-2006, 02:46 PM
With any titration test such as alkalinity or calcium hardness that uses an indicator solution the best rule to follow is keep adding drops until you get a distinct color change that holds and then add one more drop to make sure the color stays the same. When that happens don't count the last drop you added. You will soon learn what the proper endpoint is and won't need that last drop! ;)

04-02-2006, 05:13 PM
I just got back from having my water tested at Leslie's. Here's what they came up with:

pH 7.3
TA 60
CA 50
CYA 30
TDS 100
I know the TDS and the CA don't mean anything to me since I'm not using salt and have a vinyl liner pool. However, the sales guy tried to tell me I needed to add 45 pounds of Hardness + to bring my CA up. I told him "I have a vinyl liner pool, so the calcium hardness doesn't really apply to my pool." He just kinda looked at me funny. I wanted to laugh so hard!:p

So, I swung by the Commissary on my way home (yep, we're a military family) and picked up 4 more 4 pound boxes of Arm & Hammer to start adding to bring the TA up. I spent $1.80 per 4 pound box at the Commissary ($7.56 for all 4 boxes including my 5% service charge). Leslie's wanted 8.99 for a 5 pound bucket ($9.52 for each 5 pound bucket including tax).:eek: Man I love this forum! A lady at the Commissary said K-Mart had bleach on sale...I'll have to check that out tomorrow!