This evening I was doing some work on my tank and adjusting my co2 solenoid wiring, i needed a bit of extra length to reach my new plug, so without thinking I tugged on the solenoid cable. I came back 10 minutes later after going down stairs to a boiling noise. When I had tugged on the cable it had kinked my return hose, causing the external heater to boil the water above the kink as the water supply had been cut off. Below is a picture of the RIGID return pipe, which could be mistaken for a piece of flexible hosing. Accidents can happen all to easily, it was just lucky there wasn't a fire.