A friend of mine recently acquired a pipe. It is a work of art, and a pleasure to smoke through. But I was sitting there, starting to feel the smoke and thinking to myself "Wow, imagine this thing water filtered, it's a shame it's just a regular pipe."
About a week later it hit me: why not just make an attachment to filter the smoke after it leaves the pipe? I then devised this plan.
Step 2: Make a hole in the side of the bottle at the top of the label area (see diagram). The hole should be large enough to let the articulated section of the bendy straw to pass through.
Step 3: Insert the straw through the hole in the bottle, and position it so that the bottom of the straw is just above the bottom of the bottle. Be sure to leave enough clearance for the smoke to pass through easily.
Step 4: Seal the joint between the straw and the bottle well with hot glue, or your sealant of choice. Make sure that this is airtight, and sturdy. Construction is now complete.
Optional: If you want to paint the bottle go, ahead. A few notes though: Because the bottle is plastic, certain paints won't stick to the bottle very well. Obviously don't use anything toxic. Also remember to leave a stripe up the side of the bottle unpainted so that you can see the water level while filling. Don't paint the mouth or threads of the bottle, and leave the section of straw that you hook onto clean as well.
Step 5: Fill the bottle with enough water so that most of the straw is submerged. Be sure to leave at least 1 1/2 inches between the top of the water and the smoke inlet to prevent water from backwashing into the pipe.
Step 6: Attach the pipe to the straw with the hose. Be sure that the hose is long enough to let the smoke cool slightly, as we don't want the straw to melt.
Step 7: Fill the pipe, spark up, and enjoy! It might take a few hauls to prime the bong, so you probably ought to keep the bottle capped between hauls to keep from losing the prime.