Glossary
Water supply and EPANET terms as Indian municipal engineers use them, in plain English.
The same glossary, with a search box, is on the Glossary tab of Help > PipePilot Help.
| Term | Meaning |
|---|---|
| Node | Any point in the model where pipes meet or water enters or leaves: a junction, reservoir or tank. |
| Junction | A node where pipes join and where consumer demand is drawn. |
| Link | Anything that carries water between two nodes: a pipe, pump or valve. |
| Pipe | A link that carries water from one node to another, losing head to friction on the way. |
| Pump | A link that adds head to lift water to a higher level or push it further. |
| Valve | A link that controls pressure or flow at one point in the network. |
| Sluice valve | An isolation valve that is fully open or fully closed; modelled as a pipe set Open or Closed. |
| PRV (pressure reducing valve) | A valve that keeps downstream pressure at or below its setting, used for low lying zones. |
| NRV (non-return valve) | A valve that lets water flow one way only; modelled as a pipe with status CV. |
| Air valve | A valve at high points that releases trapped air. Not modelled in EPANET, but it matters on rising mains. |
| Reservoir | In EPANET, a source with a fixed water level that never runs dry, such as a treatment plant or large lake. |
| Tank | Storage whose water level rises and falls as it fills and empties during the day. |
| ESR (elevated service reservoir) | An overhead tank on staging that supplies a zone by gravity. Modelled as a Tank. |
| GSR (ground service reservoir) | A storage tank at ground level, often feeding a pump that lifts water to an ESR. |
| Sump | An underground or ground level tank that pumps draw from. |
| Elevation | Height of a point above a common datum, usually mean sea level, in metres. |
| Head | Energy of the water expressed as a height in metres: elevation plus pressure head. |
| HGL (hydraulic grade line) | The line joining the head at each point along a main. Ground above the HGL means negative pressure. |
| Pressure | Force of the water on the pipe, reported in metres of water column in metric units. |
| Residual pressure | Pressure left at the ferrule while water is being drawn. CPHEEO 2024 (Part A s.2.10.2 p.58, Table 2.7 S.No.10 p.77) asks for 17 to 21 m in Class I and II cities (17 m minimum, 21 m target) and 12 to 15 m elsewhere; rural 7 m (12 m with a flow control valve). |
| Demand | Water drawn from the network at a node, as a flow rate. |
| Base demand | Average demand at a junction before the time pattern is applied. |
| lpcd | Litres per person per day. CPHEEO: 135 lpcd, or 150 lpcd for cities above 10 lakh, plus 15% for losses. JJM rural target: 55 lpcd. |
| Pattern | A list of multipliers, usually 24 hourly values, that makes demand rise and fall over the day. |
| Peak factor | Ratio of peak hour demand to average demand. CPHEEO uses 2.5 for urban and 3 for rural supply. |
| Flow | Volume of water passing per unit time, for example litres per second (LPS). |
| Velocity | Average speed of water in a pipe. CPHEEO 2024 gives 0.6 to 3 m/s for filtered water. |
| Diameter | Internal diameter of a pipe, in millimetres. CPHEEO suggests 100 mm minimum for primary distribution pipes. |
| Headloss | Head lost to friction and fittings as water flows. CPHEEO limits the gradient to 10 m per km. |
| Roughness | How rough a pipe wall is. With Hazen-Williams, a higher C means a smoother pipe and less headloss. |
| Hazen-Williams C | The roughness value most Indian designs use: 145 for PVC and HDPE, 140 for lined DI, 100 for unlined CI (CPHEEO 2024 Table 6.2). |
| Rising main | A pipe that carries water from a pump to a tank, under pump pressure. |
| Gravity main | A pipe that carries water downhill from a higher tank or source without pumping. |
| Distribution network | The pipes that carry water from service tanks to consumers. |
| Steady state (snapshot) | A run for a single moment, with Total Duration 0. Good for checking peak hour pressures. |
| EPS (extended period simulation) | A run over time, usually 24 hours or more, so tanks fill and empty and demand follows its pattern. |
| Intermittent supply | Supply for only a few hours a day. Pressure driven analysis models it better than demand driven. |
| 24x7 supply | Continuous pressurised supply to every connection, the goal of many AMRUT and Smart City schemes. |
| DMA (district metered area) | A zone with metered inflow and closed boundary valves, so its losses can be measured. |
| NRW (non-revenue water) | Water produced but not billed: leaks, theft and meter errors. |
| Ferrule | The small fitting that taps a house connection off the distribution main. Residual pressure norms are measured here. |
| House service connection | The pipe from the ferrule to the consumer's tap or meter. |
| FHTC (functional household tap connection) | Jal Jeevan Mission term for a rural household tap that delivers at least 55 lpcd of potable water regularly. |
| Emitter | A junction outflow that grows with pressure. Used in EPANET for leaks and hydrants. |
| Pressure driven analysis (PDA) | A run where junctions receive less water when pressure is low, as in a real intermittent network. |
| Residual chlorine | Chlorine left in the water at the consumer end, which protects against recontamination. |
| Water age | How long water has been in the network since leaving the source. High age means weak chlorine. |
| Calibration | Adjusting roughness, demands and levels until model pressures and flows match field readings. |