	Applies To
	Product(s):	OpenFlows Water: WaterGEMS, WaterCAD
	Version(s):	08.11.XX.XX and higher

Problem

Is there a way to check residual pressures at a hydrant or other node for a range of flows?

Solution - Hydrant Flow Curves

With normal base demands entered for your model nodes, you can right-click on a hydrant or junction and choose "Hydrant Flow Curve". This will generate a curve of flow (demand) versus pressure. It will run several steady state simulations with a range of demands on that node, reporting the resulting pressure at the node for each one. For example, if you wanted to see how much flow could pass at 20 psi, you could simply look up the flow for 20 psi on the Hydrant Flow Curve.

For an EPS run, you can select multiple timesteps:

Nominal Hydrant Flow:

This value should be the expected nominal flow for the hydrant (i.e., the expected flow or desired flow when the hydrant is in use). The value for nominal flow is used together with the number of intervals value to determine a reasonable flow step to use when calculating the hydrant curve. A higher nominal flow value results in a larger flow step and better performance of the calculation. Note that if you choose a nominal hydrant flow that is too small and not representative of the hydrant then the high flow results on the resultant curve may not be correct since the calculation will not calculate more than 1000 points on the curve, for performance reasons.

Number of Intervals:

This value is used with the nominal flow value to determine the flow step to be used with the hydrant calculation. For example, a nominal hydrant flow of 1000gpm and number of intervals set to 10 will result in a flow step of 1000/10 = 100gpm. This results in points on the hydrant curve being calculated from 0 flow to the zero pressure point in steps of 100gpm. Note that if you have a number of intervals value that is too high then high flow results on the resultant curve may not be correct since the calculation will not calculate more than 1000 points on the curve, for performance reasons.

Time:

(applicable to an Extended Period Simulation - EPS) Choosing the time of the hydrant curve can affect the results of the curve. Choose the time at which you wish to run your hydrant curve and an EPS will be calculated up to that time. You may also select multiple times in order to generate multiple hydrant curves for comparison. Results will be different depending on what is happening at the selected time, such as the demands (based on patterns), tank levels, pump status and valve status.

Assumptions and Comparison to Automated Fireflow

Steady state vs. EPS: Hydrant Flow Curves support both steady state and EPS runs, whereas automated fireflow only runs in steady state.
Controls: If the scenario is set to steady state, both the Hydrant Flow Curve and Automated Fireflow support simple controls, if enabled in the calculation options. If the scenario is an EPS, the Hydrant Flow Curve supports both simple and logical controls. Meaning, it will run a full EPS (up to the selected time(s)) before running the hydrant run, so that controls, tank levels, pump status etc is factored into the hydrant flow curve.
Baseline demands: the Hydrant Flow Curve will replace any existing demands already on the selected node. With automated fireflow, you can choose to either add to or replace the baseline demands.
Reporting: In addition to being able to display multiple fire flow tests at once, automated fire flow will also allow you to more easily report additional details. For example, automated fire flows can account for zone pressure constraints and system pressure constraints.