Auto off water pump only when tank is full
Assume that the water is below 90% of tank. Then float switch is closed. When NO Push Button is pressed, relay turns ON. Even if NO Push button is released, the relay remains ON. Contacts 6 and 5 closes and latches the (Double Pole Double Throw) relay, to turn it off manually you need to press and release the NC Push Button. When water reaches 90%, the float switch opens and the relay is no longer latched and turns off.

If the tank is 90% full then you cannot use the NO push button to latch the relay. However the motor will run as long as you keep pressing the NO Push Button. If you need to revert to the original setup all you need to do is to use the bypass switch. The bypass switch is your traditional ON and OFF switch. Keep bypass switch in OFF position when you need auto off feature.

Choose appropriate relay rating. Hope this helps.