Please help! Going on day 10 with no or little hot water and wife and kids are ready to get a hotel room.

Facts: A 5 year old Rheem Powervent WH went out. Rheem sent gas control and vapor sensor to try to fix. No dice. Agreed to replace unit under warranty after 3 days of troubleshooting.

New WH #1:

Installed new 42VP50FN. Pilot came on, but would not light! Worst part no error code at all - just the heartbeat that everything was working great. Rheem sends new control assy (Honeywell) and new burner. I install both. No light. Rheem sends their plumber out and he does not know why it will not light. "Everything is hooked up right".
Rheem agrees to rplace with another WH.

WH #2:

Install and this time do not sweat or re-glue the 2" black ABS vent like I did for the first WH. I want to make sure the damn thing works this time. Pilot lights and no burner light! I am furious. After a good cry(kidding) I look down and see the burner that I saved from the first attempted save. I R&R the burner and what do you know...it lights up! Working great for 10 minutes and then errors out with 3 blinks "Pressure switch failed open". At this point I am about to lose it. Rheem allows me to call my own plumber (who originally installed it). He comes out and cannot figure it out either. Rheem agrees to send blower and another control valve out.

Here's where it gets fun: plumber leaves and 1 hour later heater fires up and has worked with no error for the last 3 days... but this morning no hot water and a 3 blink code! I have a new blower and controller in the box but did not do anything with it because I did not want to mess with a working unit.

After reading 2smoke's responses from this question
https://www.askmehelpdesk.com/heating-air-conditioning/power-vent-water-heater-wont-stay-ignited-418430.html

Could not gluing the ABS this time be causing the pressure switch to fail open? Could it be that easy?

Should I swap out the new blower and controller?

Please, any advice you can give is much appreciated!

How far is the vent run? What size vent is run? How many 90s and 45s are there in the vent run, and is the vent pitched correctly? After three water heaters, and numerous replacement parts, I have a feeling it may be a vent issue (most likely restricted somewhere). Of course, this is just an educated guess. I would suggest inspecting complete vent, even if you have to cut it in a few different places. Something is wrong here, and I'm betting it's a simple fix, just not so simple to find the problem. If there is any obstruction at all in the vent, it will cause the pressure switch to fail. Sorry to hear about your headache. Hopefully the plumber will keep on this and find the issue. Please let us know what you find.

Thanks... that was my first guess too. But I am just replacing a powervent that was working for 5 years. Same piping. 2 90 elbows and about 14 inches of 2 inch black ABS. And it give the same error when I let it vent directly into the garage (did this just to troubleshoot it). First thing my plumber did was blow out vent.

Have you tried the newest heater with the vent disconnected? These type of situations can be real brain teasers. You check everything you can think of, then wonder if you are just getting bad product. I know from experience that this is no fun at all. I hate to say it, but there isn't much I can do from here. I could give you all kinds of guesses, but without being there to put my hands and testing equiptment to work, I would just be wasting your time. At this point, I can only suggest that you keep after the manufacturer to pay for a plumber, yours or thiers, to stay with this until the issue is resolved. I truly wish you the best of luck with this.

Thanks... that was my first guess too. But I am just replacing a powervent that was working for 5 years. Same piping. 2 90 elbows and about 14 inches of 2 inch black ABS. And it give the same error when I let it vent directly into the garage (did this just to troubleshoot it). First thing my plumber did was blow out vent.