we bought this house about two years ago. all the work the previous owner did on the house is/was hacked at best. he redid the plumbing waste line and never hooked the stink pipe back up. also, i feel he didn't put an appropriate angle on the pipe. anyway, the toilet will not flush correctly about 75% of the time. when we first moved in the toilet flushed fine and progressively got worse over time. i believe it has to do with a lack of stink pipe, but all the other sinks and the tub drains fine. any ideas?