One way valves in the bottom of the dipper allow {HEAD ~ water} to pass into {TAIL ~ the dipper} 
to pass into
One way valves in the bottom of the dipper allow { HEAD ~ water } to pass into { TAIL ~ the dipper }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL