Algae starting - need to shock

[meatloaf]

I've notice a small amount of algae starting to grow and I need to shock. According to the Pool Calculator I need to bring my chlorine level to 18 and hold it there. My test kit (Taylor K-2005 ) will only read to 5 ppm. The testing vial holds 9 ml of water. So my question is, how many ml of pool water should I be using to perform my tests? For some reason I just can't seem to figure this out. :?
I seem to come up with an answer of approx 32 ml. Is this correct?

Thanks

 

[JasonLion]

By far the best thing to do is to get a FAS-DPD chlorine test kit. You can get the FAS-DPD test separately from both Taylor and TF Test Kits.

Using the regular DPD test kit you can measure high chlorine levels using dilution, but you lose a great deal of precision. THe way to do is to take some simple repeatable measured amount of water, perhaps a shot glass, and mix one part of pool water to three parts of chlorine free water, test that, and then multiply the result by four. The most common source of chlorine free water is distilled water. Keep in mind that using this approach measuring FC levels around 15 to 20 is going to be something like +-6 at best, and possibly much worse. For comparison, the FAS-DPD chlorine test is +-0.5.