first and second timers for cooperatively selectively energizing and deenergizing said {TAIL ~ pump} according to {HEAD ~ a predetermined schedule} 
first and second timers for cooperatively selectively energizing and deenergizing said { TAIL ~ pump } according to { HEAD ~ a predetermined schedule }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD