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Articles for Keyword "natural flow"

Construction of a Gravity-fed Water Supply and Treatment System in Developing Countries

Posted on Oct 25, 2011

This paper covers every aspect of the design and construction of a water supply system utilizing potential energy (gravity) for delivery. The typical layout of a gravity-fed water system includes a water source, transmission main, reservoir and distribution system. Every component between the water source and the reservoir is discussed in this paper, which focuses on everything related to the transmission main. This includes pipeline route survey, water resource planning, pipeline design and pipeline construction. Water treatment systems are introduced and discussed briefly. For more information on these vital components of a water supply system, refer to the sources at the end of this paper for further reading. All calculations and measurements were done using the metric system. A large majority of communities that would find this information useful use the metric system. You can read the whole document as a PDF...

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Fluid Mechanics For Gravity – Flow Water Systems and Pumps

Posted on Jun 5, 2011

A text detailing the design of water systems including the design parameters recommended for a successful and long lasting water supply. Issue 2 May 2003.

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Natural Flow Calculator Spreadsheet

Posted on Oct 25, 2011

This spreadsheet allows the user to calculate the natural flow rate (LPS) of any combination of up to 4 pipes of different diameters (in) for given pipe lengths (m) and known head (m). Microsoft Excel Spreadsheet (165KB) *** Note: this spreadsheet contains macros, and you may get a security warning.

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Part 5: Energy in a Perfect System – The Bernoulli Equation

Posted on Jun 5, 2011

Anywhere in a perfect system (i.e. there are no frictional effects), for an incompressible fluid there are three types of energy existing: Pressure Energy. Example: If you blow up the tyre of a car with a pump you are turning your physical energy of working the pump into pressure energy in the tyre. Kinetic Energy. Example: This is the energy contained in a moving fluid. If a wave hits you at the beach, you feel the kinetic energy contained within it. Potential Energy. Example: Gravity is trying to pull water to the lowest point on the earth’s surface. So when water is at a high point it contains energy, which can “potentially” allow it to flow down. At any point in a perfect system the sum of these “bits” of energy in different forms (Pressure, Kinetic and Potential) must equal the sum of these “bits” at any other point in the system. This is because energy cannot be “created” or “destroyed”, it can only change its form. This is what the BERNOULLI EQUATION expresses. Appendix 1. gives the derivation of the Kinetic Energy in terms of a pressure and Appendix 2. gives the derivation of the Potential Energy in terms of a pressure. These different forms of energy are expressed mathematically (as pressures) in the Bernoulli Equation (for a perfect system) shown below: (12) The terms on the left hand side of the Equation are as follows: P1 is the pressure energy at point 1 (expressed as a pressure). [Units are N/m2 or Pa] ρ is the density of the fluid.[Units are Kg/m3] v1 is the velocity of the fluid at point 1. [Units are m/s] g is the acceleration due to earth’s gravity (9.81 m/s/s).[Units are m/s/s] h1 is the height (from a given datum) of the fluid at point 1.[Units are m] The terms are similar on the right hand side of the Equation, but for point 2. The left hand side of the equation represents all the “bits” of energy (expressed as pressures) at a point 1 in a perfect system and the right hand side all the “bits” of energy (expressed as pressures) at another point...

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Reservoir Tank – Mould

Posted on Nov 20, 2011

The reservoir tank is placed at a point near the village that is higher than all the houses that are to be supplied. The tank must be large enough to ensure an uninterrupted supply during the times of day when there is the peak demand. The tank is thus sized according to the size of the population and the flow rate from the spring during the dry season. The tank in this system is a 13 000 litre tank made from reinforced concrete using a pre-fabricated mould. The tank has a vaulted brick roof, a method that is both cheaper and quicker than making a reinforced concrete roof. Preparing the ground for the reservoir tank. Flattening the gravel base. Adding a layer of stones to the base. Pouring the concrete base onto the prepared gravel and stone layers. Finishing the concrete base. Adding re-bar to the base to provide reinforcement. Preparing the rebar for the reservoir tank wall. Constructiong the inside wall of the reservoir tank mould. The completed inside wall of the reservoir tank mould with re-bar around the outside.. Fitting the bottom layer of the mould’s outer wall. Mixing the concrete for the walls. Filling the bottom layer of the mould with concrete. Filling the top layer of the mould with concrete. The Filled Mould. The view inside the mould showing the exit pipe. Removing the outside sections of the mould. The outside of the tank wall once the mould is removed. Plastering the inside walls of the tank. Plastering the outside walls of the...

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Small Community Water Supplies

Posted on Oct 24, 2011

This book is a very good place to start learning about building a water supply. It covers all the things that you will need to know about sourcing water including rain water harvesting, spring, wells and surface water. It also has sections on water quality and treatment. This book is made available here as PDF files. View or download the whole book in one file ( 9.8mb PDF file) 0r view the book chapter by chapter: Chapter 1: Introduction (92kb PDF file) Chapter 2: Planning and Management (124kb PDF file) Chapter 3: Small community water services in Central and Eastern European Countries – situation, challenges, needs and developments (100kb PDF file) Chapter 4: Water quality and quantity (112kb PDF file) Chapter 5: Integrated Water Resources Management (128kb PDF file) Chapter 6: Artificial recharge (636kb PDF file) Chapter 7: Rainwater harvesting (460kb PDF file) Chapter 8: Spring water tapping (1mb PDF file) Chapter 9: Pumping (500kb PDF file) Chapter 10: Groundwater withdrawal (1.7mb PDF file) Chapter 11: Surface water intake and small dams (772kb PDF file) Chapter 12: Water treatment (244kb PDF file) Chapter 13: Aeration (168kb PDF file) Chapter 14: Coagulation and flocculation (296kb PDF file) Chapter 15: Sedimentation (212kb PDF file) Chapter 16: Multi-stage filtration technology (688kb PDF file) Chapter 17: Rapid filtration (2.2mb PDF file) Chapter 18: Desalination technology (412kb PDF file) Chapter 19: Disinfection (292kb PDF file) Chapter 20: Water transmission (888kb PDF file) Chapter 21: Water distribution (1.3mb PDF file) Chapter 22: Technologies for fluoride removal (1.1mb PDF file) Chapter 23: Technologies for arsenic removal from groundwater (336kb PDF file) Chapter 24: Water supply in disasters and emergencies (1mb PDF...

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Spring Tank

Posted on Nov 20, 2011

Water is taken from a spring, rather than the river, to reduce the risk of contamination by parasites and other pernicious micro-organisms. A tank is built at the spring to ensure a continuous head of water above the start of the mainline. Thus, the mainline should always run full without any air locks.This tank is cast from conctret and consists of a sedimentation area and a 380 liter tank. Making a mould out of wood into which the concrete will be poured. Positioning the spring tank mould at the spring. Rebar is added to the mould to provide reinforcement for the concrete. Concrete being poured into the spring tank mould. Concrete being compacted into the mould. Once the spring tank is finished a dam is cast around the spring. The spring tank and spring dam. Preparing the top of the spring tank so that the roof can be cast. Making the roof and entry hatch on top of the spring tank out of reinforced concrete. The finished spring tank. The pipe exiting from the spring tank where the valve box will be. Building a retaining wall above the spring. Constructing a mould so that the valve box can be cast. Making the valve box roof. Putting the finishing touches to the valve box roof. Water flowing from the spring through a pipe to the sedimentation area. The finished spring with the dam, spring tank and valve...

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The Anatomy Of A Gravity Flow Water System

Posted on Nov 20, 2011

This section contains photographs that detail the construction of a gravity flow water system for 32 families. The system cost £130 per family and took 30 people 18 days to build. Before the system can be designed the area must be surveyed. The system consists of: A spring tank; A main pipeline, including a pipe bridge; A reservoir tank; A distribution network that leads to a tap at each house. For a gravity flow system to work properly the pipes must run full of water with no air locks. Gravity can then be used to move water, over hills and undulations, between the spring and the reservoir tank. This method works for as long as the spring tank is at the highest point in the system and that there is enough height difference, between the spring tank and the reservoir tank, to give a sufficient flow rate once friction losses have been taken into account. The distribution network also uses gravity to move water to the taps through thinner...

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The Main Pipeline

Posted on Nov 20, 2011

This system has 4 km of pipe. The main pipeline runs from the spring tank to the reservoir tank. Because of the large drop between the spring tank and the pipe bridge PVC pipe (rather than the usual polyethylene) was used to cope with the large pressures. Due to the topography a break pressure tank was not included in the design. A galvanised steel pipe bridge spansa river at the lowest point below the spring tank. The pipes reads for the laying of the pipe line. The PVC (white) and Polyethylene (black) pipe. Laying the PVC mainline from the spring tank to the reservoir tank. Joining two PVC pipe ends on the mainline. Laying the PVC pipes for the mainline. Crossing a river by building a pipe bridge. The finished pipe bridge. The Wash-out PIpe running from the mainline into the river. Building a valve box on the wash-out pipe. The finished pipe bridge, wash-out and valve...

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Water System Design Parameters

Posted on Oct 25, 2011

Condensed from A Handbook of Gravity-Flow Water Systems, Thomas D. Jordan Jnr., Intermediate Technology Publishing. It can be downloaded as a PDF. The following are a list of design parameters that are important in the design of gravity-flow water systems: Maximum Pressure Limits : The taps and valves closed state, should be the maximum pressure condition for the system. Maximum head limits for the pipe work will be used to carry out the calculations. This scenario is used at the start of the design to be able to place any break-pressure tanks that may be required. Safe Yield : The safe yield is the minimum flow from the water source. It is important to not draw more than this supply from the system at any point. If this happens then spring boxes and/or break pressure tanks will run dry and air will enter the system. Negative or Low Pressure Head : If the pressure head (P in the Bernoulli Equation) becomes negative at any point in the system then two things may happen. Firstly a siphon effect is occurring which is trying to suck water into the system. This is undesirable as polluted groundwater may be introduced into the system. Secondly, large negative pressures can cause air to come out of solution in the water and cause air-blocks. Jordan [P.52] suggests that the pressure head should, if possible, not fall below 10m (98100 Pa pressure) anywhere in the system and never go negative. Velocity Limits : The flow velocity in the pipelines should not be to great as particles suspended in the water will cause excessive erosion. Also if the velocity is too low then these particles will settle out of the flow and may clog the pipes at low points. This then requires washouts at low points in the system. Jordan [P.53] suggests that the minimum velocity should be 0.7m/s and the maximum 3.0m/s. Natural Flow : Natural Flow (see Section 8 i)) may be allowed to occur in the system at some sections of pipe. Natural flow can be problematic in that the water velocity may exceed the limits set in parameter 4 above and/or increase the flow rate above the safe yield parameter 2. Close attention should be made to these situations. Residual Head : The residual head at a tap stand or valve is important. If it’s too high it will cause erosion of the valve and if it is too low then the flow will be minimal. Jordan [P.141] suggests the following limits : Absolute minimum : 7m Low end of desired range : 10m Most desirable : 15m High end of desired range : 30m Absolute maximum : 56m Air-blocks : These occur when there are topographic features between the source and the collecting tank that are lower than the collecting tank. Energy is lost from the system as these air-blocks are compressed and can result in no flow. Jordan [P.55] gives the following design practices to avoid air-blocks : Arrange pipe sizes...

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