Are there check valves

I haven't really noticed one on my 2008 Starcraft R/T Suburban setup... If there is one there it must be external to the water heater maybe. It would most likely be only on the HOT WATER side as the COLD WATER port is used to fill the hot water heater as well. I guess there could one installed but the check valve directions would have to be different like shown in this pictorial...


I use the three VALVE BYPASS setup on mine which would not require ONE WAY VALVES I guess...


Roy Ken