How to measure dose of chlorine for disinfection of water

[cool]

Horrock apparatus is designed to find out the dose of bleaching powder(chlorine) required for disinfection of water.
contents of apparatus:
1. 6 white cups with 200 ml capacity each.
2 1 black cup
3. 2 metal spoons
4. 7 rods
5. 1 pipette
6. 2 droppers
7. starch-iodine indicator solution

procedure.
take 2g of bleaching powder in the black cup and water and make to paste. this is the stock solution.
fill 6 white cups with water to be tested.
add 1 drop of stock solution to 1st cup,2 drops to 2nd cup and so on....
stir the water in each cup with rod.
wait the half hour for action of chlorine.
add 3 drops of starch-iodine indicator to each of white cups.
development of blue color indicates presence of free chlorine.

[BCRoller]

Okay, I know this is going to sound like a VERY stupid question (blush, blush :o) but...are you referring to the chlorine that is often found in swimming pools or are you referring to something else altogether, lol? I feel like a total moron asking but, hey, I honesty don't know the answer and if I don't ask I likely never will find what I'm looking for. The reason for my asking, though, is because we do have a swimming pool in our backyard that needs to be tested for chlorine levels (before we can actually use it again) and, for the life of me, I am unsure of how to do this. So far, with all of the searching that I have done, I have never been able to find any answers that make any sense to me or have been something, in the very least, that I can even slightly understand. Call me stupid if you'd like but any help or advice you (or anyone else) can give me would be greatly appreciated all the same.

Thanx in advance. :p

From where we can buy Horrock's apparatus