The check valve for the water pump is inside the water pump and not a separate "part".. You have to replace the whole pump. I suppose you could add a separate check valve on the output of the pump. You'd have to determine the thread size and configuration and so forth.
The hot water heater relief valve depends on manufacture and model of the hot water heater. There should be a tag on the valve, under the relief release lever giving you the proper pressure and temperature ratings also.
Same with the water heater anode, some models have an anode, some don't. My Atwood doesn't use an anode. No idea what water heater was used in 2011 by PC
