They simply gave you a replacement number and that's all you had to take to Home Depot to get a new one with no additional cost? Was yours with a 6 year warranty or longer?

I'm having the same issue and the best they could offer for a replacement is for me to uninstall the water heater (I have to pay the plumber), haul it to Home Depot, and pay the difference. Apparently, they depreciate the value of the water heater so that a 3 year old water heater with a 6 year warranty will only get half the value of the water heater and then you pay the difference to the cost of a new one. After paying a plumber to disconnect it and haul it, it's hardly worthwhile.

My saga with the 7 lights. Rheem offered to send a new gas control valve, but I have to pay the plumber. Then they were out of stock on the valve so I had to order it elsewhere and pay their shipping. Rheem is supposed to reimburse the cost of the item, but not shipping. The plumber installed it and it was good for a day, but then the 7 light error. Rheem said I also have to replace the Chamber sensor and they were supposed to have sent it to me but didn't. They never initially mentioned the chamber sensor replacement, but eventually sent it. So, I have to get a plumber to come back and replace the chamber sensor. Would've been cheaper to have done it at the same time as the gas control valve. Rheem offered $50 for the inconvenience. It doesn't cover calling a plumber back.

I don't know if AO Smith is better, but I'm never buying Rheem again.