Good morning All.

I am having a problem to correlate fire flow results simulated by InfoWater and the fire flow test results collected from the field on a 150 mm Cul-de-sac watermain. Here is the issue I am facing and will be grateful if anybody could help me to sort it out:

1) Field Fire Flow Test - It uses two hydrants, one is flow hydrant and another one is residual hydrant. During the field test it flows the flow hydrant and measures residual pressure at the residual hydrant which is 90 m away from the flow hydrant. Then they provides a plot for flow vs residual pressure that necessary does not show the available pressure at the point of discharge (but 90 m apart).

2) InfoWater Fire Flow Results - We typically assign fire node and assign fire at the selected node. InfoWater provides pressure available at the fire node for the specified fire flow. It also provides available flow at the minimum required pressure at the fire node, which is 20 psi in my case. I believe, InfoWater does not know or care where the residual hydrant is (that used in the field test). Which simply means InfoWater provides fire flow and residual pressure at the point of fire or fire node.

Now the problem is, InfoWater provides fire flow and available pressure at the fire node (flow hydrant where the water is drawn), whereas the fire flow test provides flow from the flow hydrant (location of fire) and residual pressure at the residual hydrant which is about 90 m away. As a result, on a Cul-de-sac road where water is coming from only one direction makes huge difference between the InfoWater results and the filed test results. In my scenario, InfoWater results indicate that @20 psi of pressure we can have only 1100 GPM, whereas fire flow test shows we have a 1840 GPM @20 psi. Please note that the location of measurement of 20 psi of pressure is not the same, but 90 m apart. If we deduct the head loss caused within 90 m of pipe at 1840 GPM is huge for 150 mm pipe, and we end up having negative pressure at the flow hydrant (fire node).

Now my question is how to consolidate these InfoWater fire flow results and fire flow test results in order to draw conclusions whether my water system is able to provide 1840 GPM of fire flow @20 psi pressure. Our ministry, MOECC requires minimum pressure of 20 psi at any point in the distribution system during Maxday demand plus fire.

I will greatly appreciate your feedback and comments on this.


Vaughan-Mode
City of Vaughan