Any chemists here? HELP!
My wife is obsessed with bird feeders and has them all over the yard. Due to recent strong windstorms, there was a lot of seeds on the patio and after washing the patio, they have clogged the underground drain pipe. The pipe is 4-inch white PVC (it goes under the patio and out of the retaining wall). The obstruction is sitting past a 90-degree elbow, which makes it impossible for me to get it with the power washer wand (I've tried already). I also tried a plumbing snake without any success - the snake hits the clog about 6 feet in and then starts buckling, because the pipe is big enough to allow for it.
What can dissolve a clump of bird seed without damaging PVC?