Switch 1 as ground tank low water level sensor 2 & 3 as low & full water level sensors. Relay should be use 2 pole relay. Use copper rod and carbon from battery for sensors instead of switches.
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Let me explain how this circuit is working. When ground tank was full and upper tank was empty as a situation switch 1 is on and 2 and 3 switch off and relay is on and water pump will start working. When upper tank water level is over the lower state as switch 2 on and pump still working. When water level reach to full state as switch 3 also on and water pump stop working. As a same process when water level reduce and water level lower than full stage as switch 3 off but pump still running and when water level lower than empty state as switch 2 off and pump will stop working. While pump operating state if ground tank water empty as switch 1 off and water pump will stop and when water reach to sensor again pump will resume running.
