Step 1: Mark where you would like your container to have the tube placed to go into the next tube. Depending on the height of the tubes you want to connect you should determine where to cut the top off of your tube. Once you have decided how much of the top you'd like to cut off, mark it.
Step 2: Now that you've marked your jars, use a drill to make a hole where the saw will begin to cut. This part is tricky because you'll most likely be using circular pipes and it's rather difficult to make accurate circles. But don't be dismayed. Simply mark the whole a little smaller than the pipe. Then use the saw to cut the edges of the circle. This way, when you are assembling the water purifier, you will push the pipe in it will be locked in place.