1. ## Fire Hydrant Size

Fire hydrants are represented as junction nodes in InfoWater.Standard size of my hydrants are 65mm, while the model calculates fire flow analysis for junction nodes which have different sizes. my question is that how I can consider 65mm hydrant size in the model and perform fire flow analysis. Thanks

2. Hassan,

In InfoWater the Fire flow analysis is intended to tell you mathematically how much demand can be added to the model junction as a Fireflow demand and still satisfy the specified requirements for pressure. This analysis as such is "independent" of hydrant size as it is not attempting to specify the flow that would be seen when they hydrant is opened with a specific nozzle. To estimate the flow through a specific nozzle, while generally not needed for fireflow, is important when doing system flushing using UDF (UniDirectional Flushing) and can be estimated by using an emitter coefficient. A detailed discussion of how to do this and a further discussion of your specific question can be found on this thread: https://forums.innovyze.com/threads/...hlight=emitter .

The software is only going to tell you based on the model how much total demand can be applied to the model at the specified location (i.e the Available Flow) and maintain the specified minimum Residual Pressure, or it will tell you how much demand can be applied while maintaining the specified pressures as noted in the specified search range when using the Design Fireflow option (Design flow). Both of these analyses do not account for any specific nozzle at the hydrant, but are only concerned with finding how much demand can be added to achieve the specified pressures. This is usually acceptable as you are generally concerned with making sure the system pipes have sufficient capacity to bring the required flow to the hydrant rather than what exact flows will be seen from the hydrant. Actual flows seen from the hydrant will depend on the nozzle used, the length of hose connected, and if there is a pumper truck used. Since most large fires often use a pumper truck to increase the flow out of the hydrant, estimating specific flows from a hydrant are generally not considered as they would be nearly impossible to account for and would require a significantly higher amount of data to be entered by the modeler. Since, the total flow that "could" occur is generally more useful and knowing if the system mains were adequate to accomplish the needed flow is enough, this is what the model software calculates.

As noted, if you wish to estimate flow from a specific hydrant or a specific nozzle, you would have to account for specific headloss curves for that hydrant, as well as account for losses through the nozzle itself. This is very useful when doing flushing plans, but generally not critical for fire flow calculations as long as the model predicted flows exceed the required Fireflow.

Please note though that including the hydrant lateral pipelines in the model will increase the accuracy of the model predicted fireflow calculations as the hydrant lateral lines can have significant headloss associated with them at higher flows.

Patrick Moore

Originally Posted by Hassan
Fire hydrants are represented as junction nodes in InfoWater.Standard size of my hydrants are 65mm, while the model calculates fire flow analysis for junction nodes which have different sizes. my question is that how I can consider 65mm hydrant size in the model and perform fire flow analysis. Thanks