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Pipes and cisterns practice questions for bank exams

By the PrepMatic team · Updated 9 Oct 2026 · 4 min read

Pipes and cisterns is time and work with water. An inlet pipe does positive work by filling the tank, and an outlet pipe or a leak does negative work by emptying it. Questions give the time each pipe takes alone and ask how long they take together, or how a leak changes the time. The five questions below use the usual set-ups.

The method

Treat the tank's capacity as the LCM of the times, so every pipe's rate becomes a whole number of units per minute.

Five practice questions

Question 1

Pipe A can fill a tank in 20 minutes and pipe B in 30 minutes. If both are opened together, in how many minutes will the tank be full?

• A. 10 minutes
• B. 12 minutes
• C. 25 minutes
• D. 50 minutes

Question 2

A pipe can fill a tank in 12 hours. A leak at the bottom can empty the full tank in 20 hours. If the pipe and the leak work together, in how many hours will the empty tank be full?

• A. 8 hours
• B. 24 hours
• C. 30 hours
• D. 32 hours

Question 3

Pipes A and B can fill a tank in 10 and 15 minutes respectively. An outlet pipe C can empty the full tank in 30 minutes. If all three pipes are opened together, in how many minutes will the empty tank be full?

• A. 5 minutes
• B. 6 minutes
• C. 6.5 minutes
• D. 7.5 minutes

Question 4

A tap can fill a tank in 6 hours. Because of a leak, it takes 8 hours to fill the tank. In how many hours can the leak alone empty the full tank?

• A. 24 hours
• B. 18 hours
• C. 14 hours
• D. 48 hours

Question 5

Pipes A and B can fill a tank in 15 and 20 minutes. Both are opened together, but A is closed after some time, and the tank is full in 12 minutes in all. After how many minutes was A closed?

• A. 4 minutes
• B. 6 minutes
• C. 8 minutes
• D. 9 minutes

Answers and explanations

1. B. Take the capacity as 60 units. A fills 3 units a minute and B fills 2, so together 5 a minute. The time is 60 ÷ 5 = 12 minutes.
2. C. The pipe fills 1/12 of the tank an hour and the leak empties 1/20. The net rate is 1/12 − 1/20 = 5/60 − 3/60 = 1/30, so the tank fills in 30 hours. The option 8 is the wrong shortcut 20 − 12.
3. D. Take the capacity as 30 units. A fills 3 units a minute, B fills 2, and C empties 1. The net rate is 3 + 2 − 1 = 4, so the time is 30 ÷ 4 = 7.5 minutes.
4. A. The tap alone fills 1/6 an hour. With the leak the net rate is 1/8. The leak therefore empties 1/6 − 1/8 = 1/24 of the tank an hour, so it needs 24 hours. The shortcut 6 × 8 ÷ (8 − 6) = 24 agrees.
5. B. B was open for the whole 12 minutes and filled 12 ÷ 20 = 3/5 of the tank. A filled the other 2/5, which takes (2/5) × 15 = 6 minutes. A was closed after 6 minutes. Check: A fills 6/15 = 2/5, and 2/5 + 3/5 = 1.

How to prepare pipes and cisterns

• Write each rate with its sign. Plus for inlets, minus for outlets and leaks. A missing sign is the most common cause of a wrong answer.
• Let the LCM be the capacity. In Question 3, a 30-unit tank turns three fractions into 3, 2 and −1.
• Find the leak from the delay. "It takes longer because of a leak" is a standard line, so remember that the leak's rate is the difference of the two filling rates.
• Split the timeline. For pipes closed or opened midway, calculate the work done in each period separately and add. In Question 5, B's work is the simplest piece, so start there.
• Sanity-check the direction. If an outlet is open as well, the time must be longer than for the inlets alone (here, more than 6 minutes in Question 3).
• Practise alternating pipes (A for one minute, then B for one minute). Find the work done in one pair of minutes, then count full cycles and finish the rest.

Give yourself 45 to 60 seconds per question. If you are comfortable with time and work, this topic is only a change of vocabulary.

The full pipes and cisterns topic test is on PrepMatic (about 15 questions, 30 minutes). See the Quantitative Aptitude guide for how this topic fits the section, and the bank exam hub for each exam's pattern.

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