WaterCad - Inputting Hydrant Flows?
WaterCad - Inputting Hydrant Flows?
(OP)
I am brand new to WaterCad. I've done a portion of the tutorials, plus some research on the internet. Unfortunately, I've found little useful information on using the software and I have a lot of "why" questions. Additionally, the software is new to our office and no one knows how to use it.
I need to determine the static pressures and fire flows (@ 20 psi residual) of the fire hydrants on a new site. I have created the new network in Watercad using the correct pipe lengths and elevations. I connected the network to the existing system by a reservoir and pump as suggested in the tutorial. Is this the correct method to connect using the data from a fire flow test? If so (or not), how do I translate the flow data into pump data?
The data I have is follows:
FLOWING HYDRANT:85 psi static, 45 Pitot, 1130 GPM
RESIDUAL HYDRANT:90 psi static, 60 psi residual
Any assistance would be greatly appreciated!
I need to determine the static pressures and fire flows (@ 20 psi residual) of the fire hydrants on a new site. I have created the new network in Watercad using the correct pipe lengths and elevations. I connected the network to the existing system by a reservoir and pump as suggested in the tutorial. Is this the correct method to connect using the data from a fire flow test? If so (or not), how do I translate the flow data into pump data?
The data I have is follows:
FLOWING HYDRANT:85 psi static, 45 Pitot, 1130 GPM
RESIDUAL HYDRANT:90 psi static, 60 psi residual
Any assistance would be greatly appreciated!





RE: WaterCad - Inputting Hydrant Flows?
http
RE: WaterCad - Inputting Hydrant Flows?
I did solve my question though. I did away with the pump and just used the reservoir. The elevation of the reservoir was set to the sum of the ground elevation and the static pressure head. The resulting static pressures at the fire hydrants seemed reasonable based on the site conditions. Next I need to determine the fire flows of the hydrants. I am going to try making a child scenario to do this.
Thanks again!
RE: WaterCad - Inputting Hydrant Flows?
WaterCAD ships with a rudimentary user guide, which should be enough to get you through the fireflow stuff. Also, if you have tech support, in the pre-Bentley days the support was pretty good.
RE: WaterCad - Inputting Hydrant Flows?
Why would it be correct to eliminate the pump and set the reservoir elevation equal to the elevation of the hydrant + the static head? Doesn't this ignore the friction losses between the source and the hydrant? It's my understanding that the hydrant flow test should be performed so that the residual hydrant is downstream (for lack of a better term) of the connection and the flowed hydrant be upstream. From what I understand this is to estimate the available flow and the friction losses.
Also isn't the purpose of the pump curve to approximate the equation:
Q(r) = Q(f) x ((h(r)^0.54)/(h(f)^0.54))
I'm not very familiar with the fire flow option but I have a similar situation and have set up scenarios for each hydrant and assigned 1000 gpm demand at each fire hydrant node. When I run these scenarios doesn't the program just get the available pressure at 1000gpm from the pump curve and subtract headlosses to determine the residual pressure at the hydrant?
I know this isn't really worded so much as a question but I am looking for someone to tell me where and why I am wrong.
Thanks
RE: WaterCad - Inputting Hydrant Flows?
The easiest way to do this, and the way recommended by the WaterCAD manual, IIRC, is to place a reservoir at the location of the fire hydrant tested and adjust the elevation of the reservoir to match the pressure in psi that was determined in the test. If your real world situation is to have a pump downstream of the fire hydrant, then by all means use the correct pump curve, but to try to approximate a pump curve to match a pressure at a point and flow is to my garbled weekend brain not possible (needing 3 points to plot a curve when you have just two - static psi and residual psi).
RE: WaterCad - Inputting Hydrant Flows?
The equation I mentioned is a form of the Hazen Williams equation(I think, my weekend brain is garbled as well) which allows you to calculate the 3rd point of the pump curve.
RE: WaterCad - Inputting Hydrant Flows?