Gravity-Fed Water Systems 101

Water systems are a big part of EWB’s work, but have you ever wondered how many of the simplest designs technically work? Usalama team member Nick Rose explains!

Gravity-fed water systems are a relatively simple concept, though their method of implementation can make these systems more complex. Gravity-fed water systems rely only on a source of water and a difference in elevation (height) between the source of water and the consumer, such as a house, a communal kiosk, a business, etc. The flow of water melting from snow on a mountain top to a lake at the bottom of the mountain is an example of a naturally occurring gravity-fed water system. Because these systems take advantage of the natural elevation difference between the source of water and the consumer, these systems are very useful in places where there is no electricity or where electricity is unreliable (like Usalama). Because these systems do not utilize pumps and other high tech equipment, they do not require operators to have high-level technical expertise.

For a gravity-fed water supply system, the source of water is channeled through a system of pipes whose elevation gradually decreases as water is conducted towards the consumer. By directing the water through pipes of specific size and controlling its speed through elevation changes in the pipes, the team constructing the gravity-fed water supply system can design a system that provides water to the consumer at a specific flow rate.


A gravity-fed water supply system was originally designed and constructed in the Usalama community because of its ease of use and because it did not require energy or a pumping system. The system transports water via gravity from Umani Springs to five kiosks located throughout the community. The initial construction of the system did not deliver adequate water pressure for all of the the kiosks. Part of the reason for this is that, when the pipes were installed, the change in elevation between certain sections of the pipes was not significant enough to produce the needed pressure head, and therefore could not produce the desired flow rates.  The Engineers Without Borders Usalama Project Team worked with the community to redesign the gravity-fed water supply system and install piping at proper elevations to ensure a more reliable water flow when the system is active.


-Nick Rose


Learn more about the Usalama Water Rehabilitation at:

Stay tuned to read about how more than one billion gallons of cold, clean drinking water is delivered every day to New York City!


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