My mother is on dialysis 4 session was done but still she is not passing urine normally, she's passing urine like a drops. she's drinking 1ltr water in a day.

Probably normal : If she is in kidney failure, temporarily from serious insult..infection, trauma or such it is quite normal to have little or no urine. She may return to making urine later as she recovers. If permanent failure, she could produce no urine from now on. 1 liter of water per day is the necessary fluid to keep normal body functions going . Your doc can give you more details knowing the problem.