My reliance 502 gas water heater . The pilot is lite but no hot water coming out of tap?

SOURCE: my reliance sta-kleen 502 gas

Reliance is Rheem
Replace thermocouple is best start point.
Example Whirlpool manual shows general replacement steps on page 22:
Buy thermocouple at hardware or home center. measure length before going to store.
http://waterheatertimer.org/pdf/Whirlpool-6510397.pdf

Utube videos show how to replace thermocouple

Many things can affect pilot:
Low gas pressure, Water or air or debris in the gas control valve, High-heat event causing ECO to trip requiring new gas control valve, burner and tubes needing clean-out, FV sensor tripped, loose or bad thermocouple.
Manual above shows general steps for doing some of these things, but service technician is probably best choice if thermocouple does not fix problem.

Gas water heaters require periodic maintenance.
If repairs cost more than $330, then buy new gas water heater and install yourself.
Use the old one for a solar collector.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

SOURCE: reliance gas water heater, pilot will not stay

sounds like you have a worn thermocouple or maybe a blocked jet

Testimonial: "thanks for the info deaqling with it now"

SOURCE: My reliance sta-kleen 502 hot water heater is

there should be a gate valve or ball valve right above the water heater on cold side.

SOURCE: I have a reliance 805pv

OK, make sure your ON-Pilot-OFF knob is turned to "ON" after you light the pilot. Then make sure the temperature dial is not set at vacation setting. It should be set to atleast mid range between low and high at the "A" or triangle symbol, depending on what dial you have. It will take 20-30 minutes for the water to get hot, but the burner should come on right away after it has been relit. If not, you may have to call your local gas co to look at it. Douglas

SOURCE: pilot hard to lite when

The thermocouple has gone bad or in this case is going bad to the point that it is useless.

The thermocouple is the pilot's, well, co-pilot! It is the electronic device that senses if the pilot flame is hot enough to ignite natural gas or propane fuel to the burner. If the thermocouple thinks it's safe, then it keeps open the main gas valve located in the pilot assembly. If the thermocouple does not sense enough heat from the pilot flame (such as when the pilot is out), then the thermocouple shuts off the gas valve to the burners.
How the Thermocouple Works
So what is this thing and how does it work? Well the thermocouple (technically called a thermocouple junction) is a device that contains two metal wires welded at the ends and placed inside a protective metal case. The thermocouple sensor is found at the business end of the pilot flame and is designed to be placed in the hottest part of the flame. The other end is connected to the pilot valve body. As the thermocouple heats up, it produces a small amount of electricity and when it gets hot enough from the pilot, send a signal to open the gas valve by using a solenoid operated by a 24 volt transformer. The thermocouple calls the shots, and by converting heat to an electrical signal, it allows the gas valve to open or close. Once the gas valve is open, gas is then constantly supplied to the pilot and as required for the gas burners (as called for by the thermostat). If the pilot goes out, then the thermocouple gets cold and produces no electric signal to open the gas valve's solenoid and the gas valve shuts off the gas supply to the pilot and burners. Neat huh?