I been working on a 31 unit apartment remodel Building built in 1918 lots of Cast Iron. Well the deal was to re place all water lines and keep the drains. (This building sat empty for 5 years.. ) So far every stack has been full of 5 years of pipe rust and debri. (Shop vac is a good drain clearing device in this situation.) Well needless to say we was testing out the sink and it started to back up. clogged up rusted drain.. I went into the crawl space to find this line. Well I found it and had a bright idea to cut the line and unclogg it and re hook it back up. well I cut line nothing happens. I found a piece of all thread and started to poke at the clogg to see If will break loose. well after the 3-4 poke Swooosh it came pouring out. I just couldn't get out of the way quick enough. My buddy Eric thought it was funny too.