Slow Laundry Drain

Last weekend we figured out what was causing the slow drainage in the washtub. The vent pipe was blocked. A while back we'd noticed gurgling from other fixture drains when the washtub was draining, so we new there was suction being created somewhere. As you can see, the vent pipe was completely plugged with rusty scale. I cut off the bottom 3 feet of the pipe which was totally plugged. Even above that was plugged, but it hadn't packed into a solid mass. Some careful probing with a long screwdriver loosened much of it and then 5 or 6 whacks with a hammer loosened the rest. I bet we got 5 or six pound of debris to fall out of the remaining vent pipe. Now the vent pipe is clear and I've tied into the remaining pipe with ABS. Should work like a charm now.