- Read this overview of a gravity-flow water system.
- Purchase a copy of A Handbook for Gravity Flow Water Systems, Thomas D. Jordan Jr. It has a fantastic overview of the design and construction process and will help considerably at all steps along the way.
- Find others in your area that have experience designing and building water systems, especially if you are doing tank and intake structure construction. Designing a system that doesn't work is worse than no system at all because it lowers morale and wastes money. Do only what you are comfortable with taking on.
In general, the design is broken into a few areas: community census and water usage, surveying, NeatWork analysis, and individual system component design.
Community Census
The purpose of the census is to understand the projected population size for your design. If census data is available for larger communities, this may save some time. In general, for smaller communities, it's best to conduct your own census. Many times community members will inflate population estimates (a habit picked up to receive more government funding) and local government agencies have poor data.
The purpose of the census is to understand the projected population size for your design. If census data is available for larger communities, this may save some time. In general, for smaller communities, it's best to conduct your own census. Many times community members will inflate population estimates (a habit picked up to receive more government funding) and local government agencies have poor data.
The water system should be designed to accommodate projected growth. You may be able to find growth rates, but this can also be part of your census. Look at average family size. At what age are they having children? Use this information to estimate growth over the next thirty years.
Also look at other factors that may affect population growth. New infrastructure like roads or schools may mean a faster growth rate.
As part of the census, make sure that there are no other government plans or other NGO's with goals of building a water system in your community. You may be duplicating efforts.
Water Usage
The World Health Organization (WHO) recommends 30 gallons per day per person. In general, this number seems generous but can be used in designing your system. As part of understanding water usage, one should conduct a survey among a few representative homes to understand daily water usage. What activities use water (cooking, drinking, washing, gardening, animals)? When are those activities?
An example of creating a daily water usage chart is located in the gravity flow handbook.
Surveying
The gravity flow handbook has an extensive description of topographical surveying techniques. During my service, we used a simple water level and found it worked extremely well. Use a GPS, if available, with the water level survey so that you can import the data into NeatWork for the system design.
The gravity flow handbook has an extensive description of topographical surveying techniques. During my service, we used a simple water level and found it worked extremely well. Use a GPS, if available, with the water level survey so that you can import the data into NeatWork for the system design.
In general, the topography is important in tube sizing. Pressure is based on the cross-sectional area of the tube. A larger tube will reduce the pressure in the tube. (Think of putting your finger over a garden hose). Pressure is a function of height in a gravity-flow system. The higher the source or tank, the more pressure you will have down below. Elevation data is critical to sizing tubes correctly so that you have appropriate levels of pressure in community.
Survey data is also important to make sure that water actually reaches the community. In many cases, the system will go up hills and then back down as the water reaches the community. It's important to find a path to the storage tank or community that is lower than the original water source. This will ensure there is adequate pressure in the system. Again, this is discussed thoroughly in the gravity flow handbook.
NeatWork & Air in Pipes
NeatWork is a third-party software used for aqueduct design. Using survey data, NeatWork can appropriately size the tubes in the system. It also shows whether there is adequate flow and pressure reaching each home in the system. This is an important stage in the process to make sure the system will provide water to everyone.
Air can collect in the pipes between the source and the storage tank. This air can sometimes become compressed and cannot pass through the system. When this happens, an air block can actually stop water from flowing. By appropriately placing air valves, this air can escape through the valve and water can flow. Air blocks are discussed extensively in the gravity flow handbook. Though I haven't used the resource, Agua Para La Vida has a few resources on air blocks.
Individual Component Design
Individual Component Design
