Water heater needs a jump-start every morning

http://waterheatertimer.org/jpg/Rheem-Tankless-Parts-Accessories.pdf

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

Rheem does not post manuals for old products... but resources above can give assistance
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

Shut off the water and gas to the heater. Drain the heater. Disassemble the gas line to the heater starting at the Union and working to the gas control. Disconnect thermocouple, burner and pilot tunes from the bottom of the old gas control. The old control will screw out of the front of the heater. Grab the entire housing of the control and twist counterclockwise to remove. Perform new gas control install and connections in reverse. Remember to apply at least 4 wraps of Teflon tape on all threads before assembly. (Teflon paste may be used) Do NOT put any sealant on the thermocouple,burner tube or pilot tube connections (these are compression connections, make them fairly snug.) upon completion, fill heater, turn gas back on relite and check for water or gas leaks

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

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

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

Before calling service technician, read manual troubleshoot section.
It is possible there is simple do-it-yourself solution.
You posted under Universal Heavy duty 75 gallon commercial water heater.
Open following links to identify specific water heater and download manual:
The manual has wealth of maintenance information that should be done yearly by trained technician, which will genuinely help this $4000 water heater last many years longer than expected.
http://www.rheem.com/products/commercial/water_heating/commercial_gas/
http://www.rheem.com/product.aspx?id=0697944D-D79A-40C1-BDEB-875E48200DD1
http://globalimageserver.com/fetchDocument.aspx?id=c0b73553-5f03-4a5e-8789-4732ffecdccf
http://www.drillspot.com/products/155234/Rheem_G75-125_Commercial_Water_Heater?s=1

You have 75 gallon gas water heater.
I install water heater insulation 3 ways:
1) Easiest: buy ready-made blanket from Lowes and use duct tape
2) Harder: wrap heater in ordinary fiberglass insulation and use tie wire
3) Hardest: Build a box out of blue styrafoam >> leaving room for air intake for gas water heater, and space around vent pipe

Instructions for gas water heater:
Do not cover TP valve.
No insulation is put over gas valve or air intake.
No insulation touches vent pipe.
Remember the gas water heater has to breathe air into the burner, and aftter combustion takes blace, hot gases escape so extra space is left around hot vent pipe to avoid fire.

Find age of Rheem: look at 3rd and 4th digit of serial number, for example 06 was manufactured in 2006.

Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

bad gas valve

sounds as if youll need a new thermocouple

find out if it does the same noise with the venting disconnected

The dip tube which carries the incoming cold water to the bottom of the tank is bad/gone. If you can find a rheem dealer you MAY be able to get a new one but it's probably time for a new water heater