I have 2 rheem lp gas water heaters side by side and put a new pilot assembly in one but can not get either pilot light to stay lit do you have any ideas. thanks greg Thoms

The system I am familiar with uses a vapour pressure type thermocouple and if the pilot remains lit the thermocouple is working as it controls the gas for the pilot and the burner at the same time from the same source - if the gas control is ok and the flow isn't prevented by the thermostat then if the pilot remains alight, there should be a flow of gas and the burner should light - unless the gas jet is blocked or something else, some other type of blockage is preventing the flow of gas to the burner...

I suggest you check the gas jet and the flow of gas to it...

Check the pilot thermocouple. You may be able to find one at a home center.

It could be that the gap for the igniter is too big Try lighting it manually There should not be that much air in the line .

if the therocouple has packed up pilot light will not light thermocouple has long small diameter pipe leading to a larger end this needs to be above the pilot flame also for safety have a small bowl of soapy water with a brush wet the nut with soapy water in no bubbles appear then try lighting heater thermocouples don't last that long

1) Clean air intake (flame arrestor):located under combustion parts and look for broken glass from TRD
http://waterheatertimer.org/How-to-repair-Rheem-TRD.html

2) Troubleshoot by type of gas control, and link to AS Smith service manuals
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

3) Add a comment with more information
http://www.thetankatwaterheaterrescue.com/forums/forum3/

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

Following information is for tank-type gas water heater:
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot
http://waterheatertimer.org/pdf/Pilot-light-will-not-stay-lit.pdf
http://waterheatertimer.org/pdf/Attic-Ventilation-and-Pilot-Outage-in-Gas%20Water-Heaters.pdf
http://waterheatertimer.org/images/Water-heater-in-attic-800.jpg

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 .

there could be a small blockage in the pilot light gas nozzle which just need cleaning

Only thing left to change is the gas valve assembly.