a casing having {HEAD ~ a pump port}, {TAIL ~ a tank port}, and an output port, 
a casing having { HEAD ~ a pump port } , { TAIL ~ a tank port } , and an output port ,
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH