Then {TAIL ~ the surfaces} are sprayed with {HEAD ~ water} and the effluent is discarded, or recovered, if desired 
Then { TAIL ~ the surfaces } are sprayed with { HEAD ~ water } and the effluent is discarded , or recovered , if desired
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH