Have you turned the control from Pilot to On? Have you increased the temperature setting?
Spillage excessive condensate bad thermocouple draft
The thermocouple is usually the first thing to change. It controls the valve and the spark ignition is just to light the pilot.
When pilot light goes out, gas flows out of the pilot light nozzle. If out has continued for a long time, a gas cloud can develop around the furnace. When you go to light the pilot light, you'll ignite this gas cloud and make a big fire ball. If your basement is drafty, you might never get a huge cloud of gas hovering around your furnace. When you notice that your pilot light is out, you should shut off the gas to the furnace and allow any stray gas to dissipate before you turn the gas back on and light the pilot light. alliedallcityinc.com
Gas or electric? Gas, the most common problem is the thermocouple being bad. If you have a pilot light that is on but the heater will not light, that is probably the problem. Easy enough to fix. Electric, check the breaker first. It they are on, it's probably one of the heating elements burned out. Probably the top one, but it can be either. These are also easy enough to change.
If the pilot light is on, the heater should come on by itself. If the pilot light is off then it has to be lit. If it will not stay on, the thermocouple is bad.
Have you turned the control from Pilot to On? Have you increased the temperature setting?
Yes
Gas water heater has an orifice for main burner and for pilot light, if not electronic ignition.
The most common reasons for a gas water heater pilot light to go out include a faulty thermocouple, a dirty pilot light orifice, a draft in the area, or a gas supply issue. It's important to have a professional inspect and repair the issue to ensure safe operation of the water heater.
The water continues to run into and out of the water heater. There is just no flame to heat it up.
small amount
THERMOCOUPLE or defective gas valve
Same as any hot water heater. Turn the gas valve to off.
You don't. If the heater has an electronic spark, then it doesn't have a standing pilot to light. The spark lights the pilot when there is a call for heat, which in turn lights the burners. If the heater is on and the pump is RUNNING, the heater should light automatically when the water temperature is lower than the heat setting.
is the lines on the thermal coupler and pilot light for a hot water heater supposed to get hot
No, it is not dangerous. (Unless you are working with a water heater that is 20+ years old.) In any modern hot water heater, if the pilot light goes out a fail-safe will go off - preventing gas from leaking out. Also, there is a sensor so if there is not enough air-flow or oxygen with the water heater, it will shut off the gas.