You have a single valve system The valve is a 3-way valve in the COLD water line, In the photo you see the cold water inlet, coming to that is an elbow, coming to that a length of pex and that gets water from a 3-way valve, which can send water either INTO the water heater or UP to the hot line (Where it is connected with a common "T")
There is a check valve in teh HOT outlet. (the brass fitting most likely)
This is not my favorite bypass system, but it is still a good one.
Side note: if you ever find you get good cold water flow but no hot, Yet the tank is hot and if you manually open the TPR valve water gushes forth.
The afore mentioned check valve is the cluprit.