New water heater problem-wife ready to kill me.
 

Installed a Rheem Marathon 50 gallon water heater a few months ago. It only provides about 5-7 minuets of hot water then it goes to luke warm. I have replaced the thermostates I got from Rheem and the circuit breaker. Any suggestions to the cause of this problem. Wife ready to kill me Also should I have an expansion tank installed ? Thanks for your help! Ron

I'm sure you checked the temp setting on the elements? Have you checked to see if you have voltage to the bottom heating element? Sounds like only the top element is heating.

Are you sure there was a dip tube in the heater before you plumbed it in?

if it runs 5 minutes and then goes lukewarm, put your money on the lower element. could be a factory defective element that went out quick. budro

I agree with Budro. Doesn't make sense, being a new water heater & all, but it sure does sound like the lower element isn't working.

Are you sure you got the cold input on the correct fitting? Sounds like you have the input and output reversed.

Joe, thats the most logical option yet, but the OP hasn't been back so I'm thinking the wife fixed the problem:D

cHECKED AND THE WATER LINES ARE INSTALLED CORRECTLY. cHANGING OUT LOWER ELEMENT THIS WEEKEND.

check for the dip tube if you have to take the lines off. Your symptoms are typical of missing dip tube.

Fixed it last night by replacing lower element! It was easier to do than I expected! Thanks for all the help. Looking forward to keeping this water heater for a long time . Paid a premium for it since it has no metel parts all plastic and fiber glass other than heating elements and wiring. Next time, if ever, I will hook up a pump to the hose to speed emptying the heater. Ron