> *I have tried Window comparator circuit it work fine during water
> filling from 1V to 5V, but it suddenly start the pump at 4.5V*

A window comparator will do this because it doesn't have hysteresis.

So, try this dual comparator driving a D type flip-flop with a reset circuit (pretty commonly available): -



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If the sensor output becomes less than 1 volt then, COMP2's output will trigger the flip-flop (via CLK) and, because D is set to logic 1 level, the Q output will be set. 

The Q output then drives your pump (via appropriate circuitry) until the sensor output hits 5 volts. At this point COMP1 resets the flip-flop and turns the pump off. When the water level drops sufficiently, COMP2 will re-trigger the flip-flop to restart the pump.

I might be tempted to add some water overflow protection circuit as a back-up against a single failure of the circuit.