I have a Reliance 501 hot water heater, I replaced the heating element and now have only slightly warm water for no more than 5 minutes at a time. What should I do next or to test whether I need a new water heater?
You have two elements and two thermostats. You will have to check them all to see which pieces are not functioning. Any of the four will give you the problem.
You may have a defective dip tube in the water heater which is allowing the cold inlet water to cross over across the top of the tank and not become heated.