Question on Alkalinity test

[poolkeeper]

Hello all, thanks for having me

I have tested my pool for alkalinty using a Aquachem 5 way. When I add the stain to the 25ml of pool water the color is very light green. As I start adding the indicator drops the water changes from light green to yellow at around 20 drops. I was expecting the solution to turn red.

I have a very high chlorine level due to the massive amounts of shock I added to the pool to correct the algae and scum. Not sure if this is a contributor.

I have crossed checked with at Aquachek select strip. This gives me a alkalinity reading around 120.

Which method is best?

Thanks for the opinons and assistance

Pat

[GTakacs]

Ben's alkalinity test says that it will turn from blue to red or it can turn from green to orange if Cl levels are high. It does not affect the accuracy of the test. I don't know about your test kit, but I'm guessing it's the same story.

[DavidD]

GTakacs's guess and your hypothesis is right on, it's the high chlorine. Forget the strips as they are less accurate in will be hinderd even more by the high chlorine. My experience with the Aquachem though is that you are better off letting the chlorine come down before testing for anything else. The other problem is the limit at which it can test the chlorine and it does not test Free Chlorine or Combined Chlorine, just Total Chlorine (FC+CC=TC) which WILL lead to problems. My advice, buy a better test kit that will test for both. You want what's called a DPD based chlorine test kit. This forums sister site poolsolutions.com has the best in my opinion (Ps234 which test for everything) but you can also get one by Taylor (not sure of the number). The $90 bucks seams high at first but it and a constant eye will pay for itself the first season. Ben is behind in shipping so it will be a while before you get it so the sooner you order the better.

Dave