Thank you Terry and all the participants for creating such an informative website! I've learned a lot about household plumbing just by reading through the theads.
Now, I have a toilet problem that I don't know what to do about and I appreciate any advice that you can give.
I have a 3.5 gallon Kohler Handicapped High toilet (bowl is 18 inches (K-3528)) in the Master Bedroom of my parents house that I installed about 16 years ago. The toilet has never really flushed right (very sluggish, tended to clog easily, etc). A plumber in the past has pulled the toilet, snaked out the drain, and found that there were never any blockages at all in the toilet or in the main stack. There was a styrafoam liner inside the tank that was contoured with a big block to make the toilet use less water. A few years ago, after being fed up with this toilet not flushing right, I pulled out the styrafoam liner and now the toilet uses about 4 gallons of water to flush.
This seemed to solve the problem at the time, but in the last year, the toilet has started flushing sluggishly (water just barely getting enough swirl to make everything go down). The toilet is using the maximum amount of water it could use. I've determined that there isn't a blockage in the the main stack as the toilet in the bathroom on the opposite side of the wall which shares the same stack line flushes like a charm. I took two five gallon buckets of hot water and dumped them down the toilet and everything went down at rapid speed. I also snaked out the toilet and there were no blockages.
I have noticed that there seems to be some small bits of black, sewage gunk that seems to back syphon into the toilet bowl when everything goes down after the toilet flushes. It only happens on this toilet. Do you think the trapway is heavily corroded? I know the trapway is unglazed.
There appears to be no blockages.. Is this just a bad toilet? I really don't know what else to do, as I would like to save this toilet as they don't make 18 inch bowls anymore. Any advice would be greatly appreciated.