My upstairs toilet still flushes, but the water doesn't leave fast, so that
the bowl fills up and empties slowly, and ends up less full (of water) than
usually. It also gurgles (outside where the vertical drain-pipe is) halfway
through.
I have a heavy vertical iron drain-pipe outside, which has the bit that
sticks up in the air for venting. At the bottom, there is a horizontal
underground run for about 3 meters, at the end of which is a manhole where
everything seems ok.
I worry that the underground bit has collapsed, and I will not be able to do
that myself. I also generally worry about the heavy iron venting pipe (in
case it falls), which is right over where we sit outside in the summer.
Questions:
1. What is likely to be wrong ?
2. What can you do if the underground bit has collapsed ?
3. How heavy is the iron pipe likely to be (per foot), if I want to try to
take it down myself ?
4. Do you know any drainage plumbers near Ruislip (west London) to AVOID, or
perhaps recommend ?

Many thanks...