Rheem powervent ignites then goes out, electronic ignition.

Tank is rusted out:
Replace tank
http://waterheatertimer.org/Leaking-water-heater.html

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) Rheem-Richmond does not post service manuals:
Copy following link to identify service manual by type of gas control valve:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

2) For lockout, the air intake might be clogged or combustion parts dirty, causing overheating which will break TRD glass vial. Gas control may need to be replaced. Reset gas control by rotating knob to lowest temp for at least 6 seconds.
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html

3) Call Rheem or local service tech.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) Copy following link to troubleshoot by type of gas control valve:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

2) Replace gas control valve.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

`1) Copy following link to troubleshoot by type of gas control valve, blower motor links, pressure switch testing, and other professional resources:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent
http://www.thetankatwaterheaterrescue.com/forums/forum3/

2) Power-vent blower motor can go bad.
Plug motor directly into outlet, or turn on-off switch on, and see if motor works.
Check outlet for correct polarity, and for at least 80% of rated voltage.
Check vacuum switch. Blower creates vacuum, and the vacuum switch detect vacuum, and signals gas control valve that burner sequence can continue.
Gas control valve can also go bad. Wiring etc can go bad.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Hello
You need to unlock disply by holding down the up and down buttons until the lock flashes then goes away.

Once inlocked you can press mode button to resume normal operation.

Here is a link for your HW heater.Note pgs 22 to 24.

http://globalimageserver.com/fetchDocument.aspx?id=a92c7d0e-8a95-48ba-8810-cd714f33d47a

Start-point is to inspect and clean burner parts and combustion chamber, clean air intake, bleed air out of gas line, test gas pressure, test electronic gas control valve, check for venting issues.
As general rule, gas water heater manuals recommend professional service once a year that would cover most items listed above.
To see images, and for more reading and resources, look at your product manual and open following link:
http://waterheatertimer.org/How-to-install-gas-water-heater.html#clean

Richmond/Rheem sells power vent blower assembly that cost about $300.
Your product manual shows part numbers.
http://www.monstermarketplace.com/heating-supplies/rheem-sp12562-blower-assembly-powervent-2
Replacement gas control valve costs $300

just an educated guess but id say you have one of two possible problems , gas valve bad or flame proof device is bad

the second cause is very common !! so common in fact theres a spare hanging on the side of mine !!!

CHECK THE POWER VENT UNIT

Is the water heater in a basement or an area thats cold? A water heater jacket may help.

If not ,try setting the heat up a little higher on it until you have more then a 5 min hot shower.

May pay you to get a 100 gallon heater.

Possible igniter trouble. Should get an expert and watch him and see what he does. That way the next time you just might be able to repair it.