Well, another benefit to tieing into the drain valve port is simplifying the inlet to the heater. When you think of what has to go on that line: check valve, shutoff, exp tank and maybe a union....makes me want to pipe to the drain, if only for the sake of the next poor sod who'll have to deal with it.
Now, the stacking and stratification I was speaking of concerned a certain type of commercial wh. They are bottom-fed, high efficiency commercial units. Units without circ pumps have a tendency to stack---where layers of water of different temperatures exist within the tank. Kind of like when you've swam in a lake (if you have) the shallower water is warmer than the deeper portions. The pumps I've installed in those cases was to stir this up, so that the tank is closer to a uniform temp.
But it makes no difference, besides what I've outlined above, to dump your recirc into the inlet of a top-fed heater. It is getting the water down to the bottom of the tank. I just find it better to keep the inlet piping clean, and get a better drain valve at the same time.
--Customers of plumbers: Never be afraid to ask for proof of licensure of the plumber servicing your equipment. A licensed plumber will be proud to show you his personal license.--
Hope this thread is still active. I just installed my return line to the bottom of the tank. I also put the pump (Watts 500800) in the return line because I didn't want to potentially limit the flow on the hot side. Water circulates fine but as I shower the water gets progressivly colder. I had assumed I was drawing cold water up through the return line, but I believe the pump has an internal check valve.
#1. Is it possible the temperature at the top of the tank is being diluted that quickly?
#2. Am I, in fact, drawing cold water backwards through the running pump?
#3 What about plumbing the return line back to the top of the tank, not through the dip tube inlet, directly to the top.