This is the typical looking water pump....
These can be installed anywhere... Mine is located next to the water heater tank.
I have seen them under the sink and also accessible from the pass thru storage area.
I guess you know where it is by the sound it makes when you use it...
You may have to remove a panel to get to it. It won't be permanently hidden from view but may be behind a panel you can get thru by removing some screws...
This one shown in this google image is installed on the floor next to the water heater tank...
Sample photos from GOOGLE images
Roy Ken