On Thursday, January 23, 2014 10:51:51 PM UTC-5, wrote:
I vote for a couple of gallons of boiling water, not just hot water, poured down the drain followed by a whole gallon of clorox. Do all this while the disposal is running.

Yes, this.

My last house was built in the late 40's and the cast iron pipes would start running slow every now and then. A pot full of BOILING water thrown down the sink, tub, and laundry sink would sort it. Just greasy buildup from everyday stuffs. We didn't have a disposer but we did have a dishwasher.

nate