Water Clock Experiment

Water Clock Working Principle

Clocks have been in use for several centuries of human existence to measure time. While it is known that mechanical clocks had come into existence in the 13th century, it is believed that the first people to make use of devices to tell time were those from Egypt and Iraq. The accurate time, when these devices were invented is unknown but they worked on the principle of the position of the sun and thus were called 'sundials' otherwise known as sun clocks. Over time, sun clocks became more and more accurate and were extensively used until the late nineteenth century. It was during 1400 BC that water clocks saw light. These sophisticated instruments, invented by the Egyptians, have marked a new invention in human history.

What is a Water Clock

In simple words, a water clock is an instrument that uses the flow of water to measure time. They are quoted as one of the earliest time measuring devices that did not depend on the observation of celestial bodies. The earliest water clock was found in the tomb of Amenhotep 1, who was buried at a time around 1500 BC. Early water clocks consisted of bowl-like stone vessels that allowed water to drip at a constant rate from a small hole at the bottom. Hours were measured using markings in the inner surface of the container.

More mechanized and sophisticated water clocks were developed between 100 BC and 500 AD. They had a better regulation of pressure, leading to a more constant rate of flow. This was the era that also saw water clock designs, that was fancier with small figures of people or birds popping out to signify the passage of an hour. Other improvements were the changes in pointers and adjustments in dials.

Types of Water Clocks

There are two types of water clocks. They are:

  1. Outflow water clock- In an outflow water clock water fills up a container and drains out of it after the time it is designed to signify. An observer can distinguish the time by following the markings on the container which holds the water.

  2. Inflow water clock- An inflow water clock works on a similar principle to an outflow water clock except that after the passage of time water flows into the container rather than out of it. Here an observer could follow the level up to which water has filled up to tell the time.

Water Clock Working

A water clock works by using the controlled flow of water to time. There are several types of water clocks that work in different methods. The working of a simple water clock consisting of bowls is elucidated.

  • The bowls of a water clock would be arranged in series.

  • At noon all the bowls would be empty.

  • Each successive hour, one bowl would get filled.

  • After the completion of an hour, water would overflow from the lip of a bowl into the next bowl.

  • The detection of the passing of an hour, half, and quarter of an hour would be simple using this method due to filling up and markings respectively.

  • However, to accurately point out 5 minutes and more precisely each minute would be a difficult task requiring mastery.

How to Make Water Alarm

The steps involved in making a water alarm are elucidated below.

Things Required:

  • Three bottle caps

  • Unusable sketch pen

  • Buzzer

  • Superglue

  • 9V battery and connector

  • Aluminum foil


  • Glue together two bottle caps such that they resemble one.

  • Make holes through the pair of caps, the third cap, and a piece of aluminum that is of similar size, such that the holes are just enough to fit the sketch pen into them.

  • Stick the sketch pen to the third cap.

  • Glue together the two caps duo to the foil piece.

  • Fit the caps duo and foil to the pen and affix them on the other end of the sketch pen.

  • Use a piece of plastic to prevent the cap from falling.

  • Fix one end of the buzzer to the negative terminal of the battery.

  • Glue together the positive terminal of the battery and the other end of the buzzer to the bottle caps at either end of the pen using connecting wire and small pieces of aluminum foil if necessary.

  • Partially immerse the pen in water with one cap floating on water and one cap affixed at the top of the water container.

  • Set a water clock using this container to measure time.

  • Adjust the cap on the top of the container to the desired time to ring the alarm.

FAQ (Frequently Asked Questions)

1. What is the Water Clock Working Principle? 

On neglecting the viscosity of the liquid used, (here it is water) the basic physical principle a water clock works on is the Torricelli's law. 

The Torricelli’s law also known as the Torricelli’s theorem states that "the speed of a liquid (v) flowing under gravitational force out of the opening of a tank is equal to the square root of the product of vertical distance between the liquid surface and the center of the opening (h) and to the square root of twice the acceleration due to gravity (2g)."

2. How to Make a Simple Water Clock?

Here is the stepwise procedure for making a simple water clock project.

  • Take an empty container with a reasonably sized hole on top and fill it up with water. (The hole ensures that a vacuum is not formed due to excess pressure.)

  • Take another empty container and a marker that writes on this container.

  • Place the water-filled container overhead of the empty container and pierce a small hole using a paper pierce or a safety pin which allows the regulated flow of water through the water-filled container.

  • Using a stopwatch measure and mark the water level filled for each minute on the empty container.

  • After this is done this setup can be used for measuring time without a clock.