Pipes and cisterns is an easy yet an important and marks gaining topic given in the aptitude test. Pipes and Cisterns are almost like Time and Work questions. This is a quite straightforward topic yet very important topic from aptitude point of view as the questions on this subject are usually given in a number of competitive examinations including, Campus Recruitment Tests, Banks Entrance Exams, Management Entrance Tests and Other Competitive Exams. In pipes and cisterns problems, it is require to identify the amount or portion of the tank each of the pipes fill or drain in unit time (say in a minute / hour / second) and after that do arithmetic operation on the given value.

Rules for Pipes and Cisterns

Inlet is referred to as the pipe which is supposed to fill the tank.

A pipe that is meant to empty the tank is called as outlet.

When a pipe works for x hours for filling up the cistern, then 1/x portion of the cistern will be completed in 1 hour.

When a pipe works for y hours to empty the cistern, then the portion of the cistern emptied in 1 hour is equals to 1/y

Pipe A might fill a cistern n times as quickly as another pipe B. This states that if slower pipe B works for x min to fill the empty tank, then quicker pipe A works for x/n min to fill up the empty cistern. If they work collaboratively, then the portion of the cistern which is loaded up in 1 hour is (n + 1)/x