Testing for high CL levels with drop kit

My test kit, as most do I suppose, only reads to 5 ppm Cl. When I am trying to kill algae, how do I test for Cl levels at shock level, i.e. 15 - 20 ppm for my stabilizer level?

Thanks,
Ed

Dilution..

Carl recommends a shot glass with 1 part pool water and 3 or 4 parts distilled water.

However many parts you have is what you multiply the reading by to get your actual level.

For example:

1 part pool water + 3 parts distilled water = 4 parts water

Multiply your reading by 4 and that will give you a good sample of the pool.

You must use distilled water--steam-distilled water is available at most supermarkets and discount drug stores--a gallon is cheaper than a gallon of bleach!