A small amount to keep the pilot light going.
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.
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.
Have you turned the control from Pilot to On? Have you increased the temperature setting?
No, that is where you put it to light the pilot light. That is the only thing that will come on at that setting.
Gas water heater has an orifice for main burner and for pilot light, if not electronic ignition.
The gas will shut off and the heater will not work. Modern heaters do not have a pilot light but ignite the gas each time it is needed (this saves on gas).
Same as any hot water heater. Turn the gas valve to off.
THERMOCOUPLE or defective gas valve
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.
is the lines on the thermal coupler and pilot light for a hot water heater supposed to get hot
The water continues to run into and out of the water heater. There is just no flame to heat it up.
The thermocouple is bad. That is the small tube that sits in the flame of the pilot light and runs to the control valve. Easy and cheap to replace.
If the tub is not getting hot water the issue is probably with the hot water heater. The hot water heater may have tripped a breaker or the pilot light went out.
If it is gas operated, the hot water heater may not light because it may have a defective millivolt sensor. The millivolt sensor is heated up by the pilot and generates a fractional amount of voltage telling the gas valve that the pilot is lit and the gas valve can now be safely opened to heat the water heater.
Thermocouple is most likely the problem but it also can be wind and draft which blows out the pilot light and very rare it can be you have a air pocket in your line or sometimes condensation can drip on the pilot. If you have a flame when starting the pilot light as you are pushing down on a non forced air gas water heater and the pilot goes out after you release the pilot handle then 90 out of a 100 times its your Thermocouple. If you have a forced air tank type gas water heater it can be a lot more sophisticated and I recommend you read your manual trouble shoot guide and follow those steps for YOUR specific water heater.
low back, spillage, or a bad thermocouple.
Most pilot lights are not adjustable. If it's not working properly the usual solution is to change the thermocouple.
Pilot light alone will not produce enough heat to damage the tank, but the main burner will destroy the tank and possibly start a fire. Why would anyone want to leave the pilot light on an empty tank?
To infinity and beyond. Without pilot light, burner will never turn on to heat water.
Gas not turned on to water heater. Gas valve on water heater not set to pilot setting. Faulty gas valve. Igniter for lighting pilot not working.
Spillage excessive condensate bad thermocouple draft