I want to know the age of this water heater serial # GELN0701102676

Add a comment and include brand, model, type and approx age of water heater for possible help.

http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html

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The gas control is leaking gas around the knob?
The gas control needs to be replaced before causing explosion and/or fire.
Gas control has identifying marks on side.

Water heater is not 100% identified.
Unknown if this is gas or electric heater.

Problem posted under Whirlpool water heaters typically made by American water heater company.
Call Whirlpool 877-817-6750.
They will ask for model number and serial number located on label on side of tank.
Call is answered in USA by trained person who can answer specifics about that model, including warranty, age, regular maintenance, error codes, and possible solution for that specific model and serial number.
I have found these folks to be helpful.

Whirlpool manuals do not show that specific model:
http://www.whirlpoolwaterheaters.com/support/manuals.aspx

If you have the energy smart electric water heater with electronic control board, then error code explanation shows on the control board. Error 1 or a single flash, is start-up failure and requires tank to be full of water. Read page 10 of manual. Make sure water heater is full of water and water is coming full stream out of tub spout before turning on power. Also disconnect power from unit, make sure water heater is full, and then reconnect power to see if unit resets.
http://waterheatertimer.org/Whirlpool-Energy-Smart-electric.html
http://www.whirlpoolwaterheaters.com/downloads/6510306.pdf

Are you asking about tankless gas or tankless electric?

You posted under Tankless gas water heater: gas type tankless plugs into standard 120Volt household outlet to power circuit board. You need larger gas line than used for tank-type gas water heater.

If you are asking about volt and amp draw of Tankless electric, then that depends on specific model number.
For example, if each tankless element draws 3500Watts, and unit has 3 elements, you will need 3 additional 20 amp 240Volt circuit breakers. Volts x amps = watts. 3500 watts divided by 240Volts = 14.58 amps. At full blast, this unit would draw 43.75 amps and will cost more to operate yearly than tank-type electric water heater. If unit has 4500 watts elements, then it will draw 56 amps at full blast, and use a good percentage of household power.

Tankless water heaters have no hot water in power outage. This is true for gas and electric models.

Additional resources:
http://waterheatertimer.org/images/Compare-water-heater-parts-650.jpg
http://waterheatertimer.org/pro-n-con.html
http://waterheatertimer.org/pdf/Bradford-White-on-demand-tankless-service-manual.pdf

Leaking propane is red flag #1 and fire hazard.
Immediately update your insurance and then turn off gas.
If pilot is not staying lit, then gas leak can be cause of pilot problem since pressure on the line is reduced.
Other causes include bad gas control valve, air in the gas line, bad thermocouple, burner parts need cleaning, or all the above.
After fixing leak, replace thermocouple, clean combustion chamber and burner parts, and bleed gas line to remove air.

More resources:
http://waterheatertimer.org/Atwood-water-heater-resources.html

State, Kenmore, Reliance, Ace , Ambassador, Barnett, Century, Crosley, Energy Stretcher, Freedom, Freedom/Nipsco, Hardware House, Master Plumber/True 5, Mission, Nationaline, Patriot, Penfield, President, Regency, Century, The Plumbery, Thermo-king, TopLine
1-letter month followed by 2-digit year

So it was manufactued in 1994. Most water heaters will last 5-10 years for gas and 10-15 for electric unless they receive yearly maintenance (flushing tank, cleaning) so it is already past its expected life span.

That being said, an electric water heater is more costly than a gas one. If I was in your place I would start saving to replace the unit with a tankless gas water heater, as soon as the house closed.

You posted under Rheem gas water heater.
GP can be gallons-per-minute
I believe you have tank-type gas water heater from description of gas valve:
Information is on label on side of tank showing Brand, type, BTUs, model number, and serial number.
Gas valve information is located on side of gas valve:
http://waterheatertimer.org/images/04128.jpg

Since water heaters vary widely, the best place to start troubleshooting is manual for your specific model.
Open following link to identify product. Click on water heater that looks like yours, and next page has pdf files where you can download install-operation manual.
http://www.rheem.com/Products/tank_water_heaters/gas_water_heaters

Search pdf for the word 'ON' or 'gas control'
In any case the manual should be digested fully to gain understanding of your specific water heater.

Once you identify product, re-post question on fixya or the tank, with link to manual, to see if more information can be gleaned from experts and professionals

Also post a photo of your gas valve for possible identification by expert:
http://www.fixya.com/support/r6568559-post_photograph_fixya_questions_answers

Find age of water heater using serial number
http://waterheatertimer.org/pdf/WaterHeaterSerialNumberDecoder.pdf

If you have Rheem tankless: open following link:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Add a comment for more free help.
Also 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.

Reliance makes gas and electric water heaters.
http://www.reliancewaterheaters.com/

Best way to start is to look at label on side of tank.
Label has serial number, model number, plus it will say if heater is gas or electric.
Reliance water heater age is shown in serial number: first digit is letter, second two digits are numbers: for example numbers 02 would be the year 2002.
If water heater is 8-12 years old, it might be time to consider new tank.

Gas water heater has 3 inch metal flue pipe coming out of top of tank.
Gas pilot is probably off.
Relight pilot light: Most gas water heaters today have instructions on side of tank just above gas valve that say how to relight pilot light. Instructions vary by model.
If you have gas water heater that is older, it might be easier to call a plumber.

Electric water heater has panels on front.
Open top panel and push in red reset button.
If you have electric water heater of any age, you can usually fix it yourself same day:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

12 year old water heater is getting near the end.
Some tanks last 20 years, but that's the exception.
To find exact age of your brand water heater:
http://waterheatertimer.org/pdf/WaterHeaterSerialNumberDecoder.pdf

Leaking TP valve:
1) Lift TP lever and gently lower back into position to see if that stops leak.
Occasionally something gets stuck in the valve.
2) Sometimes water heater temperature gets turned up because heater is not producing as much hot water as before, and higher temps cause TP to release pressure because of overheating.
Dial temperature down to 120 degrees.
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html

3) If steps above don't fix problem, replace TP valve >> TP valves have 125 or 150 degrees rating >>> older tank shouldn't be running above 125 because higher temps cause more pressure on tank, so thermostat should be lower than 125 degrees TP rating.
Buy replacement TP at any hardware store + a roll of teflon tape to seal pipe threads.
Turn gas control to pilot ... this will keep pilot lit but burner will not fire.
Let water cool, and then drain some water out of tank.
If TP valve is on side of tank, then open drain on side of tank and drain water until it is lower than valve level. Open bathtub spigot to let air into line.
http://waterheatertimer.org/Water-heater-will-not-drain.html
Be careful around water that is higher than 120 degrees F >> you can get burned quickly >> apply cold water to any burn.
Use pipe wrench and unscrew TP valve counterclock-wise.
Install new TP and put teflon tape on threads.
Re-fill tank completely and open tub valve on hot side until water is running >> then turn gas control back to original position.
Do not fire up any water heater before tank is completely full of water or this could damage tank.

To read more preventative information about water heater leaks and age problems:
http://waterheatertimer.org/Water-at-bottom-of-water-heater.html

the system was not sized properly, you need to have a 3/4 gas line to the unit for the volume of gas it needs, the tankless water heaters need to have every bit of gas that is says, it sounds like who ever installed di not make sure you had enough gas comming in the house, you might have to either have a new meter installed or run the gas lind directly from the meter to the water heater and cap off the gas line thats there