Journal of Pipeline Systems Engineering and Practice

Over 10,000 failures have occurred in US oil and gas pipelines in the past 15 years, highlighting the significance of safety measures for such facilities. Various models have been proposed by researchers to predict different failure parameters. Despite such efforts, no comprehensive review has yet been conducted in this domain. The objective of this study is to provide a detailed review of the methodologies proposed to predict failure parameters for oil and gas pipelines. Such a review gathers, organizes, classifies, and analyzes previous contributions in this domain and highlights the gaps associated with different failure prediction models. In addition, the current code-based methodologies for predicting the failure of oil and gas pipelines and their corresponding limitations are discussed. As such, this study provides pipeline operators and researchers with a comprehensive overview of the research and practices in oil and gas pipeline failure and safety. In conclusion, several avenues for future research are discussed. In particular, a maintenance planning procedure directed by pipeline availability analysis is proposed to address the existing gaps and limitations.

Microbiologically induced deterioration (MID) of concrete sewers is a common problem that requires a considerable amount of rehabilitation investment every year. MID is the result of dilute sulfuric acid dissolving the cement matrix. The acid is produced by a complex series of chemical and biochemical reactions. Hydrogen sulfide (${\mathrm{H}}_2\mathrm{S}$) is produced by sulfur reducing bacteria (SRB) in the liquid phase, and then in time, this gas is converted by sulfur oxidizing bacteria (SOB) into sulfuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$). The last conversion occurs above the liquid level under aerobic condition. The objective of this study is to present a literature review and authors’ experience on progress acquired over years in understanding causes and effects of MID of concrete in municipal sewerage systems, methods to prevent and control MID from happening, and rehabilitation of already damaged pipes and structures. Published papers were identified that directly or indirectly reported MID of concrete in sewer structures over a period from 1980–2018. The literature review and authors’ data suggest that deterioration of concrete is a complex process that involves varied surface interactions. Many empirical inputs that vary with installation and repair of various structures have been identified. The addition of liquid antimicrobial additive per standard procedure shows resistance of concrete to MID. Additionally, results show that resistance of concrete to MID increases with increase in the mixing time of the admixture. Further research is needed to study the concrete–microorganism interactions to have a better understanding of the microbiologically induced culture that leads to concrete deterioration in the sanitary sewerage systems. Additionally, there is a need to identify and develop more effective coatings, and safe antibacterial agents that can be used during construction of sewers to inhibit colonization of SOB over the exposed portion of the sewers.

The feasibility and effectiveness of basalt fiber reinforced polymer (BFRP) wrap in the rehabilitation of corroded pipes under bending and internal pressure was investigated by using experimental tests and numerical analyses. The experimental program consisted of eight pipe specimens with diameter-to-thickness ratio (D/t) of 34.5 tested under four-point bending and internal pressure. Corrosion defects were simulated on specimens by reducing the wall thickness. The corroded specimens were repaired by using BFRP-composite wrap. The numerical modeling, conducted by using a commercially available program, studied the effect of the fiber orientation of BFRP wrap and the number of layers of BFRP wrap. The results indicated that increasing the amount of BFRP layers can successfully increase the bending capacity of the pipe, and there is an optimum thickness of BFRP fabric. When the findings of this study were compared to the current guidelines, it was found that this standard does not take the ovalization effect of in-plane bending into consideration.

This paper presents the results of studies of water hammer phenomena in a physical model in combinations of two and three pipelines connected in series. The combined pipelines were made of steel and polypropylene. Pipelines made of one material type were connected in series in different configurations of diameter ratios and lengths of connecting sections. The obtained results were used to verify the value of the equivalent celerity calculated from equations derived using linear analysis of natural vibrations of the system. For verification of the equations, an algorithm in MATLAB was developed that allows one to easily calculate the equivalent celerity, $c_e$, for $N$ pipelines connected in series with varying diameter, length, and material composition. The ability to easily determine the value of the equivalent celerity allows the calculation of the maximum increase of pressure for a given configuration of pipelines, for example, after pipeline modernization or during making decisions on the installation of often expensive equipment to counter the negative effects of water hammer.

Traditional optimization methods of heated oil pipeline operation are usually offline or nondynamic, where steady-state models or complex and inaccurate physical models are utilized. To achieve online optimization with high adaptability and timeliness, this paper deploys a neural network (NN) to identify and imitate a real thermal and pressure response system instead of solving complicated model equations. The NN is trained and built by pipeline history data obtained from the Supervisory Control and Data Acquisition (SCADA) system. For a certain pipeline, real-time operating parameters like pressure and temperature are predicted by the NN once the inputs are given. Three different neural networks, a backpropagation neural network (BPNN), radial basis function neural network (RBFNN), and general regression neural network (GRNN), are compared to demonstrate their error-control abilities when predicting those parameters. Then the parameters are sent to particle swarm optimization and differential evolution (PSO-DE) optimization units to calculate the costs. The NN identification and PSO-DE optimization are applied to the Rizhao–Yizheng digital long crude oil pipeline. Experiments demonstrate that the three NNs have similar prediction accuracies, and the RBFNN and GRNN have better prediction stability than BPNN. Most of the prediction errors of the flow, outlet pressure, and inlet temperature can be controlled below $50{\mathrm{m}}^3/\mathrm{h}$, 0.1 MPa, and 0.1°C, respectively, and the online optimization is achievable. The maximum reduction of the total energy cost is 10.75%, and the saving effect is significant.

The increasing number of corrosion-based incidents in pipeline systems within recent decades has encouraged decision makers to focus on predicting when pipelines will fail, and to improve maintenance strategies. Policymakers and pipeline operators need to frequently evaluate and renew existing failure prediction models and maintenance strategies. Accordingly, this research accomplished the following two objectives: (1) it developed a predictive failure model for internal and external pipeline corrosions, and (2) it developed a model to determine the optimal timeline for maintenance policy, when the corresponding costs can be minimized. For this analysis, data were collected from 11 natural gas transmission pipeline failures that occurred between 2001 and 2011 in the United States, and were categorized into two groups based on their internal and external corrosion levels. Then the homogeneous Poisson process (HPP) and the nonhomogeneous Poisson process (NHPP) were implemented to evaluate the reliability trend of pipelines. The results revealed that the trend of pipeline reliability was deteriorating for both external and internal corrosions, except for a few cases that showed improvement and stationary trends. Additionally, the decade of installation and types of corrosion were recognized as significant causes of pipeline failure. To find the optimal replacement time, a cost-effective model was developed to determine the latest time that maintenance can be scheduled before the cost of the maintenance increases. The results of this study will help decision makers in the pipeline industry accurately predict the number of failures in pipeline networks, and wisely select the most appropriate maintenance policies.

To provide efficient pigging operation, a stable and moderate speed of the pig is preferred. This paper describes a brake device for controlling the speed of a pig in a gas pipeline. A pigging model of a pig with a brake unit in gas pipeline is presented. In the model, the relevant pig speed equation is combined with the gas flow equations. It is assumed that the velocity of gas at the tail and nose of the pig is equal to that of the pig. Moreover, the inlet flow rate and the outlet pressure are kept constant during the simulation. The method of characteristics (MOC) is applied to solve the transient equation of gas flow, and the Runge–Kutta method is used to solve the pig speed equation and the steady flow equations to obtain the values of initial flow. Two cases for pigging simulation were carried out to verify the performance of the brake unit. The corresponding results indicate that the brake unit can prevent undesired high speed of the pig when the pig restarts under a stoppage condition in a gas pipe. Additionally, a brake device can ensure a more stable speed of the pig. However, due to the drag force generated by the brake unit, a greater differential pressure between the tail and nose of the pig is required to drive the pig in motion.

Leaks in water distribution systems can run continuously for extended periods undetected due to their minimal impact on pressure and vibration signals in the overall system. Detecting such leaks from acoustic measurements is challenging because leak-induced changes in acoustic measurements can be masked by strong background noise or usage-induced changes. This paper addressed the problem of leak detection and localization in water distribution pipes through a technique called linear prediction (LP). LP was shown to be effective in capturing the composite spectrum effects of radiation, pipe system, and leak-induced excitation of the pipe system, with and without leaks, and thus has the potential to be an effective tool to detect leaks. The relatively simple mathematical formulation of LP lends itself well to online implementation in long-term monitoring applications and hence motivated an in-depth investigation. A data-driven anomaly detection approach was presented which utilizes the features extracted from the LP coefficients representing the underlying acoustic signals. In terms of leak localization, compared with correlation techniques using raw signals, it was shown that shorter segments of LP reconstructed signals can achieve similar levels of accuracy as those using longer segments of raw time series, which is a key advantage in long-term online implementation applications. A relatively complex experimental test bed was used to generate realistic acoustic data under various hydraulic conditions, including simulated leak and flow cases. Most importantly, due to the simplicity of the technique, this method has significant potential for autonomous leak detection and localization in full-scale monitoring applications.

Two corrugated steel pipes were repaired with grouted high-density polyethylene (HDPE) slipliners, one with low-density (i.e., low-modulus and low-strength) grout, and the other with high-density (i.e., high-modulus and high-strength) grout. The responses of the rehabilitated culverts were measured under service loads and fully factored design loads, as well as even higher load levels, to establish the ultimate limit states. Finally, the test culverts were exhumed and the damage was observed. Sliplining increased the stiffness of both culverts, and their strength then exceeded the required load carrying capacity by more than a factor of 2. Although the lined pipe with low-density grout behaved like a rigid pipe during service loading, it began to behave more flexibly at higher loads. At very high loads, the liner deflections exceeded levels permitted for HDPE pipes. Extensive shear failure and crushing of the grout were observed after the test. The sliplined pipe with high-density grout behaved like a rigid pipe during both service load and ultimate load experiments. Distributions of hoop strain through the liner–grout–steel pipe system demonstrated bonded, composite behavior at some sections of the system repaired using high-density grout, and noncomposite behavior for the system repaired using low-density grout.

Buried water pipelines are subjected to corrosion deterioration and are vulnerable to extreme events (e.g., earthquakes). Corroded metallic buried pipelines have experienced severe damage during past earthquakes resulting in the service disruption of Water Distribution Systems (WDS). Also, continuous and adequate water supply is imperative for fighting fires caused by earthquakes. Therefore, evaluation of the functionality of WDS and its service restoration after an earthquake is very important for the water service provider as well as communities. This paper presents a framework to evaluate both component-level and system-level seismic risk and resilience of WDS considering time-variant corrosion of pipelines. The vulnerability of individual pipelines is modelled by modifying the American Lifelines Alliance (ALA) pipeline vulnerability functions to explicitly account for the strength deterioration due to corrosion. Resilience is modelled using a functionality curve that relates system failure probability and repair activities over time. Probabilistic functionality fragility surface (FFS) is developed for both components and system by integrating the fragility curves and the restoration functions. The use of the proposed framework is demonstrated on two hypothetical water networks, one small scale and one medium scale. The results of the two case studies show that the restoration process has a significant influence on the shape of the FFS. Time to repair a break, number of breaks, network topology, the level of corrosion, and the available resources of utility companies are key parameters that determine the shape of the FFS. It is also observed that larger and older WDS networks experience a significantly higher number of breaks, which compromises their resilience. The proposed framework provides a useful planning tool for asset management of WDS subjected to seismic hazards.

It is common in practice to utilize finite elements for obtaining a solution for soil–structure interaction problems. There are different finite-element methods (such as implicit and explicit) being employed at present to understand the behavior of buried structures. Implicit finite-element solutions, which are unconditionally stable, are more common to use for soil–structure interaction in spite of excessive analysis time, memory usage, storage requirement, and converging issues. On the other hand, an explicit finite-element method that uses dynamic finite-element formulation is conditionally stable, but can be used to analyze soil–structure interaction problems under quasi-static conditions. This paper describes an overview of the two solvers and how they can be used to analyze soil–structure interaction problems using buried pipeline as an example in Abaqus. The paper also elaborates how the explicit method can be used to model the behavior of unsaturated soils under undrained conditions. User-defined advanced constitutive models were developed to capture the behavior of dry, partially saturated, and fully saturated soil behavior in conjunction with implicit as well as explicit platforms. The results of the developed codes in Explicit are validated by comparing with the results of the equivalent coupled pore fluid diffusion and stress analysis using simulated single-element triaxial tests. The developed codes in the explicit algorithm were also verified against the results obtained from physical triaxial test data and large-scale pipe–soil tests conducted in dry as well as in unsaturated soil mediums. The formulated models under explicit algorithms provide great benefits that include fast simulation time and less numerical problems for conducting three-dimensional finite-element simulations on soil–structure interaction analysis.

Soil restraint development during relative ground movements is an important consideration for assessing the integrity of buried pipelines. Evidence from full-scale experiments suggest that the relative backfill particle size with respect to the pipe size may influence the development of lateral soil restraints. In experiments in which pipes buried in uniform significantly coarse-grained soil backfill were subjected to relative movement perpendicular to the pipeline alignment, the lateral soil restraint increased to a peak value and the backfill experienced a block-type failure mode; with increasing displacements, some of the backfill mass disintegrated and flowed as individual particles, leading to a postpeak reduction of lateral soil restraint. When pipes in backfills with relatively small particles were subjected to relative lateral movement, the backfill moved as blocks, without disintegration as individual particles. It was shown that full-scale soil–pipe experiments can be effectively simulated using numerical discrete-element modeling (DEM), including the particle-size effects on the lateral soil restraints and ensuing soil failure mechanisms. Using the DEM work, considering a range of pipe diameters ($D$), burial depths ($H$), and mean backfill soil particle sizes ($d$), it was possible to delineate $(H/D)\text{-}(D/d)$ combinations that constitute pipeline configurations leading to significant postpeak reduction of lateral soil restraint during ground movements—a useful consideration to select optimal backfill materials to reduce soil forces in pipeline design.

The article describes a preparation method and performance behavior of polymer composite systems with a matrix of low-density polyethylene (LDPE) and a reinforcing agent of Taurit. Taurit (a kind of shungite) is an inexpensive, well-available, and environmentally friendly mineral that is compatible with many polymers. The composites have been prepared via extrusion blending, and their mechanical and protective properties have been studied. The performance of Taurit-containing materials has been compared with properties of composites with other commonly used fillers (e.g., carbon black, talc, aluminum oxide, and asbestos fibers), and Taurit has proved to be the most efficient reinforcement in this series. The results indicate that the obtained composites can be used as coatings of pipelines to protect them from corrosion and mechanical damage.

Glass fiber–reinforced plastic (GRP) pipe was aged in different environmental conditions to investigate its morphological structure, mechanical properties, and thermal behavior. In the oil field service, the durability of nonmetallic pipes is questioned considering exposure to different harsh operating conditions such as high temperature, ultraviolet radiation, and rain. The influences of different environmental condition parameters can affect the properties of GRP pipes and, consequently, impact their overall performance and service life. In this study, samples subjected to similar conditions of the desert field revealed a noticeable tendency of wet crude oil at sufficient water cut to cause degradation to the GRP tubing material. Scanning electron microscopy and thermographic analysis of samples subjected to long-term exposure in the aquifer water revealed the formation of salt crystals. The two-phase crude oil/water system under nonultraviolet radiation samples showed no significant diffusion by the chemical media. The tensile testing showed a slight change in tensile strength with aging in wet crude. In addition, samples exposed to ultraviolet radiation have revealed an evident change in modulus results, in which the polymer matrix of samples subjected to ultraviolet radiation and elevated temperature is most affected. Our results show that the mechanical properties of the composite pipe samples aged in wet crude were more deteriorated than those aged in harsh water, and for surface pipes ultraviolet radiation has an impact on the stability of the polymer matrix after a long exposure period.

An experimental investigation on the hydraulic transport of sand particles in pipelines is presented in both horizontal and 30° upward inclined orientations. The pipe, with an internal diameter of 0.0254 m, had sand transported in various water superficial velocities at low and high sand concentrations [0.1%–10% volume-to-volume ratio (v/v)]. Sand particles were polydisperse (144–250 μm) with a $d_{95}$ of 210 μm. The minimum transport condition (MTC) was determined by means of video recordings and pressure gradient (PG) measurements. MTC and PG were observed to increase with increase in sand concentration and mixture velocity. At high sand concentrations, there was a decline in PG with decrease in flow velocity until a minimum is reached around the MTC. The MTC at which this occurs is different in the two pipe orientations. Based on a previously reported dimensionless relationship, a correlation was derived now including the effect of pipe inclination using extensive literature data in addition to the current. The effect of key flow, geometric, and particle parameters were adequately captured in the improved closure relationship for sand minimum transport conditions in pipes.

In this study, the effect of coating disbondment gap size on corrosion and electrochemical conditions of the X-52 pipeline under simulated tape coating disbondment protected by cathodic protection (CP) was investigated. In this regard, corrosion cells simulating coating disbondment with gap sizes of 5, 3, and 1 mm and also a steep disbondment with a slope ratio of $5/1$ [5 mm at the open mouth (OM) and 1 mm at the far end from the OM] were used. Different levels of CP were applied to the OM of the simulated coating dibondment using a three-electrode system, whereas pH and potential were recorded under the simulated coating disbondment at different distances and, also, time intervals. Results showed that depending on the CP potential level at the OM of the coating disbondment and disbondment gap size, there could be variations in corrosion and electrochemical conditions on the pipeline surface under the disbonded region. In fact, with a decrease in coating disbondment gap size, lower pH and higher levels of CP were observed. However, under narrow disbondment (gap sizes less than 1.6 mm), despite the better CP, significantly higher corrosion rates (more than 500%) were observed. This was explained by a crevice corrosion mechanism.

Water infrastructure plays a crucial role in delivering freshwater for survival and economic prosperity of communities. Regrettably, drinking water pipeline infrastructures in the US and many other developed and developing countries are in a deteriorated state becoming increasingly prone to leakages, which are estimated to be $\ge 20\%$. Although several sensor-based leakage-monitoring systems already have been developed to address this pressing challenge, the sustainability of such monitoring systems was never cross-checked, especially in the context of monitoring large-scale water-distribution systems. This paper thoroughly studies the life-cycle aspects of a vibration-based leak-detection technique, namely leak-detection index (LDI), accounting for its cost and energy consumption. The capabilities of this new technique have been demonstrated previously through an experimental campaign. In this paper, a follow-up sustainability evaluation is conducted after conceptual prototypes are developed for the real-world deployment of this new leakage-monitoring system. Batteries and solar panels are considered options for power supply. A representative water distribution network is used for estimating the life-cycle cost and energy consumption of leakage monitoring using the proposed prototypes. The sensitivity of cost and energy consumption to data sampling rate, data transmission rate, and sensor spacing are also evaluated in this study. The results presented in this paper will be of interest to researchers working on sensor-based monitoring systems for water infrastructures and to water utility managers.

Water main failures cause water disruption, damage and flooding to roads and buildings, inconvenience to daily activities, and significant economic loss. There are few studies on economic valuations needed to justify aging water pipeline improvements. This study aims to assess the benefits of aging pipeline improvements using economic valuation techniques (e.g., damage cost avoided method) for intangible benefits and to develop an economic feasibility study framework for water pipeline improvement programs. The economic feasibility study framework was robust and reliable in a pilot test. Thus, the outcomes could help water utilities conduct better economic feasibility studies on aging pipeline improvements, revealing previously unknown social benefits in monetary values. This framework will promote proactive water pipeline management in order to prevent costly water service outages. The most significant benefit in economic valuation of the study site (i.e., the benefit-cost ratio) was the reduction in public distrust, followed by economic loss and future water demand. The least significant benefit was found to be sustainability improvement through the reduction of ${\mathrm{CO}}_2$ emissions.

The Colebrook equation gives the Darcy-Weisbach friction factor for fluid flow in pipes as a function of sand-grain roughness and the Reynolds number. Values of equivalent sand-grain roughness ($k$) have been obtained for various ductile iron pipes coated with different anticorrosion materials through fluid flow experiments, and the results show that the value of $k$ calculated by the Colebrook equation varies significantly with the Reynolds number. Considering the uncertainty in the hydraulic data due to errors during lab measurements, the paper shows how to estimate a reasonable value of $k$ based on a systematic analysis of uncertainties for a pipe of given diameter, length, flow discharge, and head loss, as well as width, height, and head above the crest of sharp-edged weirs used for flow measurement. The values of $k$ for three pipe cases were estimated, and rules pertaining to uncertainty in the relevant parameters and the Reynolds number are summarized with quantitative relation expressions. A sensitivity analysis of the estimation of $k$ and some important practical findings are also provided.

An estimated 20% of treated fresh water is lost through leakage in distribution pipeline infrastructure in the United States. As a result, significant research has been devoted to developing technologies that will assist water utilities in detecting and locating leakages in their distribution systems. The authors recently developed and demonstrated a technique referred to as the leakage detection index (LDI) technique to determine the presence of leakage through temporal comparison of the cross-spectral density (CSD) of pipeline acceleration response measured at multiple locations along the pipeline length. One major limitation of the experimental setup in the previous study was the lack of soil backfill. Consideration of the backfill is important because it could alter the vibrational features of the buried pipeline. In this study, the authors determined the effect of the surrounding soil backfill on the vibrational characteristics of a buried PVC pipeline and subsequently determined the influence on LDI for various leakage severities. A comprehensive experimental campaign was conducted using a two-loop PVC pipeline test bed comprising multiple pipe sizes, multiple bends, T-joints, and valves. Multiple cover depths and multiple leakage sizes were investigated in this study. Confirming our hypothesis, the results revealed that the soil backfill intensifies the dampening effect of pipeline vibrations. Furthermore, irrespective of the soil cover depth, the LDI metric exhibited a monotonic increase as the severity of the leakage increased, and it could be further developed to be suitable for leakage detection in real-world buried PVC pipelines.

Scour valves in a water distribution network are used to remove sediments that get deposited in the pipe and also to drain off water whenever it gets contaminated. The main governing factor associated with the design of a scour valve in a large water distribution system is the time of emptying water from all the connected pipes as quickly as possible. The network located in the flat terrain requires a driving head preferably at the source that can empty the volume of water available in the entire pipe network under the action of scouring velocity. It is customary to locate the scour valves at the lowest elevated points if the network is in a hilly terrain. In contrast, in the case of flat topography, such a location is seldom available. This paper presents a simple approach to size a scour valve based on the time of emptying the chosen portion of network and also to find the number of scour valves needed and its nodal location to drain off water simultaneously from the network having a flat topography. To solve the formulated optimization model for scour valve design, a differential evolution (DE) optimization algorithm was applied to minimize the number of scour valves required to drain off the water within a stipulated time. Hanoi and Apulian networks are considered to illustrate the proposed approach for optimal location and sizing of scour valves. The results of the optimization have shown the appropriate locations and optimal size of the scour valves.

With the consistent increase in the global population, sustainable construction has become a trend that will need to be practiced in perpetuity. The three main factors of sustainable construction that should be considered during planning and design of new projects are direct cost, social costs, and environmental impacts. Direct costs are regularly evaluated, and social costs are coming under more scrutiny, but the environmental sustainability of construction is a big issue due to increasing concerns about global climate change and carbon emissions. If reducing carbon emissions is a target, it is first essential to quantify the environmental impacts of any potential project to set the target to achieve. In the pipeline industry, carbon footprint analyses for the construction phase have been performed regularly to identify less-carbon-intensive methods. The pipeline industry, however, has yet to evaluate the environmental sustainability of its construction materials during the fabrication stages. The objective of this study is to calculate and analyze the environmental sustainability, as determined by carbon footprint and embodied energy, of 30 m (100 ft) of pipeline during the fabrication stages (material extraction, material production, and pipe manufacturing). This study focuses on three commonly used types of pipe/pipeline: prestressed concrete cylinder pipe (PCCP), PVC, and cured-in-place pipe (CIPP). This paper focuses on a large-diameter 90-cm (36-in.) sewer pressure pipe operating at 689 kPa (100 psi) internal pressure. Results show the environmental sustainability of PCCP to be lower than PVC and CIPP. The second phase of this project will focus on the environmental impacts for each material during construction and operation to determine the overall environmental footprint of each material.

A mechanical-based approach was applied in this study to evaluate the operational risk of water mains in the Shanghai region. First, a pipeline’s structural performance in terms of stress indicators and structural failure criteria were determined by the mechanical-based approach. Second, a comprehensive parametric study was carried out to evaluate the variation of operational risk of water mains at different periods. Finally, the evolving operational risk of water mains in the Shanghai region was evaluated. The accuracy and applicability of the mechanical-based approach were validated by reviewing recorded accidents. According to the investigation, the mechanical-based approach is an efficient method to evaluate the operational risk of water mains. The operational risk level of water mains grows with increasing exposure due to corrosion of wall thickness. In applications, the mechanical-based approach can be extended as an early warning system for city officials to improve day-to-day operational conditions. Consequently, an appropriate maintenance scheme can be designed to make the rehabilitation of the entire water supply network economical.

A water supply gravity main does not require power input; thus, it is preferred in comparison to a water supply pumping main. Moreover, a gravity main has greater reliability because it does not have moving parts, e.g., pumps and motors, and is independent of power requirement. Availability of a regular power supply at a required current and voltage is a problem in many parts of the globe. For a gently sloping topography, the gravity main involves large pipe diameters. Thus, in comparison with a pumping main, a gravity main may be uneconomical due to large size and associated overall cost. A review of the literature indicated that there is no guideline available for the adoption of a gravity main for a gently sloping terrain. In this investigation, a criterion has been obtained to ascertain if a gravity main or pumping main will be economic for a given gentle terrain for pipe laying.