Calibrating a model in WaterCAD using Flow Test Data

[head22]

Hi,

I'm relatively new to WaterCAD and modeling in general, and there's no one in my office who knows enough to answer my question, so I turn to you all.

I've built a model of a small municipal distribution system and am trying to calibrate it. I have results from a flow test done last year that gives the location of each hydrant along with "Static Pressure" "Residual Pressure" "PITOT Pressure" and "Hydrant Flow"

The tests were taken over a period of three days from 8AM to 5PM.

I know the general approach is to adjust the roughness coefs to try and match the observed pressures with the calculated pressures, but I'm not sure how to go about this in WaterCAD. Should I run a Steady-State simulation and manually adjust the flows & roughness coefs? or should I run a 72 hr extended simulation & use the Darwin Calibrator (which I have never used)

If anyone has experience with this, I would appriciate any information.

Thanks

 

[Sterilecuckoo58]

There are two things flow tests are good for - approximate assessment of system condition and identification of gross inadequacy. To perform the assessment on paper you need two flow rates and two pressures. Doing the test during the day means you have background flow, do it 3 a.m. and you may neglect background flow (unless a day tank is being filled - but thats much easier to get an estimate for given line)

I used to use a pumper truck and have them run two flows - 150 gpm or so and as high a flow as they could get without dropping residual too much.

So pick a few choice runs, figure out a roughness and run with it. Calibrating a system and trying to match results strikes me as time wasted given the lack of accuracy of the flow measurements.

If your clients system is sluggish or if they have bad flow test results, look for closed or partially closed valves, undersized lines, dead ends (yeah some of them are not so obvious).

If house pressures are down, look at the behavior at the spigot, a burst and then low flow means you have a small orifice, and I will never forget that the corporation stop itself can be the culprit...

It has been a while since I have used a simulation program so my opinions are jaded.

Never assume: valves are open; checkvalves are there; wiring is right; pipes are connected; and that there are no brick walls in your drainage pipe.