There should be a float that tells it when to come on and go off. The float is probably stuck and this keeps it running. The float will normally be either something sticking out on an arm or a ball like device connected to a rod that can go up an down. Find the float and wiggle it and then let it drop. It should shut off and then you have to find why it was sticking.

thanks,

i looked for a float valve.

but what i learn now is i have a submersible pump with
diaphram switch.

to my knowledge diaphram switch works on pressure sensing
and does not go up and down.

so can you please let me know what should i do to get rid of this problem.

problem: pump drains out water and does not stop after doing so.

thanks,
avani

Not sure what kind of submersible this is. Some submersibles that I've seen still have a visible float. On your pump there has to be something that activates the switch. If it's pressure sensative it would seem that somehow it's either stuck or defective. Maybe you can take the switch apart to see where it's stuck. If that doesn't work it sounds like you will have to replace the switch.