I have a Rheem PG50T9A hot water heater that is leaking. It seems to be spraying water from the vent tube in the heater. I shut the gas and water off and am now dealing with the damage done to my kitchen ceiling. Any ideas on what may have happened?

There is no pilot light on your power vented hot water heater. You may as well unplug it because the induction fan will continue to run. Hopefully your propane company is responsible enough to perform a gas leak check on your propane system. After the gas is turned back on, you can plug in your water heater to start it up. Run-outs are costly so it's bet to get on automatic delivery or call when the tank is down to 30%

Copy following link to troubleshoot by type of gas control valve:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html
http://www.thetankatwaterheaterrescue.com/forums/forum3/

Rheem does not post service manuals ... wonder if that's why huge majority of water heater problem on fixya are about Rheem/Richmond tank and tankless water heaters

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

Call Rheem:
1-800-432-8373

For error code 11 troubleshoot:
http://waterheatertimer.org/pdf/Rheem-Ruud-Error-code-11-2008.pdf
For more Rheem tanklesss resources:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

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

Water on top of gas heater can be caused by poor venting, or inadequate combustion.
Make sure water is not coming up from under tank top, indicating tank leak requiring tank replacement.
Have a plumber look at problem to make sure home is not filling with deadly, odorless CO gas.
Inspect pipes that they are not corroded and covered with condensate.
Check that roof cap is in place.
Let heater fire and burn for a few moments so the fire is going good, and then light match just outside the draft hood on top of heater. Blow out match and see if smoke draws immediately into vent and upward.
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html
http://waterheatertimer.org/Leaking-water-heater.html

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

If pilot lights and flame is robust and clear blue, and pilot goes out later, then some suspects can be excluded: air in gas line, low gas pressure, thermocouple is overtightened (finger-tight + 1/4 turn), thermocouple not positioned correctly in the flame, dirty pilot tube.
If flame is yellowish and small: then clean pilot tube and combustion parts.
http://waterheatertimer.org/How-to-install-gas-water-heater.html#clean
Remaining suspects can include: air in gas line, low gas pressure, bad gas control valve, tight house so household vent fans pull air down water heater vent that blows out pilot, hot attic with inadequate ventilation, water dripping down vent.

Open following links to read troubleshoot resources.
http://waterheatertimer.org/pdf/Pilot-light-will-not-stay-lit.pdf
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot

Hopefully just the thermocouple. The thermocouple is the small rod right next to the pilot light. The flame on the pilot heats up the thermocouple and keeps the gas valve on. You can replace it yourself. The thermocouple will be connect by a small nut on the underneath side of the valve, and you will have to pull the thermocouple out of the pilot assembly. Not an expensive part, you can get it at any hardware store. Hope this helps you .

A leaking water heater cannot be repaired, assuming it's the tank leaking and not nearby water pipe.
http://waterheatertimer.org/Water-heater-leaking.html

First thing is to protect your property from catastrophic tank failure where tank ruptures and water runs until it is shut off:
Tanks are under pressure when they are hot.
Close cold water shut-off located above tank.
Turn control knob to 'pilot' so pilot is lit but burner will not turn on.
Open hot side on tub for few moments to relieve tank pressure.

Now your property is safe.
You need a new water heater.
In mean time, gas water heater makes 41 gallons hot water per hour.
Shower used 5-9 gallons hot water.
Bath uses 10-15 gallons hot water.
You can turn on water heater for short stretches and limp by until you get a new heater.

Steps for installing gas water heater:
http://waterheatertimer.org/How-to-install-gas-water-heater.html

There could be blockage in your water heaters venting on the outside of the home. It sound like the high limit switch has been tripped. Try unplugging the tank and plugging it back in. this will reset the tank. if the problem persists you will want to call your provider for service.

I was having the same problem untill I reallized it was my venting system. Test the water heater with no vent on top. Disconnect the vent pipe from the water heater and try turning on the hot water. the water heater needs a special adapter to vent the direct vent water heater. One other thing you can check is the gas pressure in your home. You have to have between 7 and 8 WC (water Column) for the tankless water heaters. You can call your gas supplier to find out what you have.