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