I'm looking for help with this installation. My water heater is a long way from the master bath. My contractor said a recirculation line from the end of the hot side back to the bottom of the water heater would reduce the time it takes for hot water to reach the master bath. Several attempts have failed.The system will circulate hot water. The problem is that when you turn on the hot water it never reaches true hot status. If I close the recirculation line the water will get to max temp. I think it is because it is drawing water from the return line. They have installed a check valve near the water heater but it does not seem to help. Does the location of the check valve matter? My plumber and I are getting frustrated. Any thoughts?

It is almost impossible to "retrofit" a recirculation line into an existing system without a pump. The ENTIRE system has to be designed for it, and an existing system would NEVER be properly designed. The location of a check valve, with or without a pump, IS important.

i have run many recirculation lines with no pump all have been successful.
the check valve should be a swing check installed in the horizontal position and close to the tee inserted between the drain valve and the tank. set the check valve so it stops the flow going away from the heater drain. drill a 3 /16 inch hole in the check valve gate.
insulate all the piping but leave off the last 18 inches or so of the insulation at the return end. this will help the return end to cool faster so the action of convection will work better. it is the difference in temperature between the hot and cold that makes the water move.
lastly, make sure there is no rubber flow check in the hot nipple at the tank.
it will take a few hours for the circulation to get going but once it gets going , good old mother nature will make it work just fine..

Hot water rises. As soon as the piping goes downward, the circulation stops. If ALL the piping is horizontal in a basement, then it may work.

Hot water rises. As soon as the piping goes downward, the circulation stops. If ALL the piping is horizontal in a basement, then it may work. VERY few homes in AZ have basements, and MOST have MANY place where the hot water goes "up and down" preventing thermal circulation, hence a pump.

What is the reason for the hole in the check valve gate?

The circulation flow is weak and maybe not enough to open the check valve. The small hole allows the convection circulation, while limiting the backflow.

I don't think the check valve is the problem. I know water is circulating back to the tank because the line gets warmer when the valve in the recirculation line is open. The problem is when I turn on the shower it does not get as hot as it should leading me to think water is drawing back from the recirculation line. When I close the recirculation line the water gets hotter which seems to prove my theory.