Got a toilet that keeps blocking? find out why, and have one of our experts inspect the problem today! Get quotes from our selected suppliers by only filling in form! Turn off the boiler and disconnect it from the power supply. Dump the hot water down the drain so that it can melt away some of that grime and any hardened grease if this method appears to work for the clog, continue doing so until you've got the drain cleared! Office of energy efficiency & renewable.