20 Most Recent RTO Waste King AH-780-UL Quick&Hot Instant Hot Water Dispenser - Tank Only Questions & Answers

Your heating element was over-heating and was a fire hazard at this point. I have the same unit, same problem. If on "High" the heating element will over heat and melt the connectors. If left too long can cause a fire. There are other's with the exact same issue.This was an old post, but I replied to help any new individuals searching for similar problems. (May 2022)

That center connection uses a clamp. You made no mention of the clamp in the post. Did you get a clamp with that unit? IT is a squeeze clamp and you put it over the inlet tube and connect the tube to the unit and then slide the clamp down to the connection and open the clamp and continue sliding it down over the nipple on the tank and then release it.

Should be a place on the bottom of the unit to insert a hex or allen key to turn it to break it free... if its jammed. Make sure power is off/ disconnected prior to performing this task.