Hose-end Drain Unclogger

This is a printable take on a tool from the "big box" home improvement centers, which you put on the end of a hose and stick into a clogged drain. When you turn on the hose the bladder -- toy balloon in this version -- expands to make a seal against the inside of the pipe while a jet of water pressurizes the drain and clears the clog. The commercial version works quite well, but costs over US$20 and I've blown two of them out by applying too much pressure.
This version can be modified, if you'