The water heater will cycle 5-6-7 times with no probles then it fails ignition. The water heater is a rheem 50 gal power vent 2. It is about 2 years old.

http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#pressure

3 flashes, failed pressure switch?
Test pressure switch
Gene

Water Heater Timers Save Money

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

www.rheem.com/products/tank_water_heaters/contact_support

1) I believe you can immediately elbow the PVC pipe.
There is a limit for how many elbows can be used between blower and termination, and limit is determined by diameter of PVC pipe.

2) Copy following link for venting resources and typical Rheem and Richmond power vent manuals, and diameter-elbow pdf from Bradford White.
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#venting

3) Richmond is Rheem. Product manual will show specifications for venting.
Product warranty is voided if installation does not follow specifications shown in manual.

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

Why is it always Rheem problems?
Every water heater problem is Rheem.
And Rheem doesn't post any service manuals, like the other two big manufacturers, AO Smith-American, and Bradford White.

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

Scroll up and find pressure switch heading among links.

You can install gas control valve yourself.
http://waterheatertimer.org/pdf/How-to-replace-water-heater-gas-valve.pdf

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

(sometimes) is hard troubleshoot on an electric water heater,possible there is a voltage issue,such as time usage of appliance for cut rate pricing?

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.

1. Turn off power vent blower and set water heater temp to vacation (lowest temp)
2. Turn on power vent blower
3. Turn the water heater temp from vacation (lowest temp) to hot (highest temp) four times.
4. Set the water heater temp to normal

Don, if you have done this before go for it. If not call a pro,you will thank yourself later!

if you have the exhaust run together it will not light up,, they have to be seperate,, the computer board sences the unburnt gasses and will not allow it to start,,