One action during the delay

Is there a way to ignore delay, when the moisture sensor detects low water,it turns the pump on ?.

yes, use a timer based on millis();.

See Using millis() for timing. A beginners guide, Several things at the same time and the BlinkWithoutDelay example in the IDE

How to use millis()?
millis(2000);

millis(2000);

No

See the links in post #3