Not sure I really understand it's purpose- is it like a methane gas detector, where you know that once you have smoke, fire is imminent, and to get the heck out of there?
Put the hamster cage in the quietest place in your house and just bring the hamster back to it's normal place after all the commotion.
The nipples are short sections of pipe (about 4-6 long) that are on the top of the water heater. They connect the water heater to the cold water input and the hot water output lines. Other things to check is the water valve that controls the water going into the water heater - it should be fully open. Do you have good water flow from other fixtures? If you do, then it's not the water heater, but the individual fixture. Make sure the control valve is not partially closed or plugged with debris.
