EPA NET Reservoir

[jeepeng]

Hello all,

New to EPA NET and this site and I have a question.

I'm mimicking a model which was performed and approved utilizing Water Cad. I'm using EPA NET and will "tie" onto this system with my proposed system, so I thought I would make sure I could get the same values that the water cad model produced. My nodes are almost exact for pressure and head, my flows and velocities on the other hand are way off!

It starts at the reservoir from what I can tell. My reservoir has a Net Inflow of -258, (I'm assuming this is the total calculated demand from the system?) I do not know anything from "their" reservoir other than the HGL. My first pipe is a 24" dia, 6,250 l.f. roughness of 150 (HW) and it's producing 258 gpm with a velocity of 0.18. Their first pipe is the same design as mine but produces 953 gpm with 0.68 fps velocity.

This difference is obviously effecting my entire model. Also, it is a "floating" system so no pumps. I guess I'm supposed to assume and endless supply at an static hgl.

My question is, how can I increase my flows out of the reservoir?

Does what I wrote make sense?

Thanks in advance.

 

[Pinwards]

It sounds like the difference is in the demands applied at your nodes, or the demand Pattern (you can apply peak factors with a pattern), so the total demand/flow out of the reservoir is not equal to the original model. Having the same pressure/head means you probably have the node elevations set correctly, but the difference lies in your demands.

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[jeepeng]

Pinwards,
First thank you for responding. Second, I went back and double checked my demands and they are identical to the model I'm attempting to mimic. I have no demand patterns set up yet as I wanted to do an average day demand prior to adding in Maximum hour demands as well as fire flow demands.

Any other thoughts?

Thank you!

 

[77JQX]

Where does their additional flow go? If the nodal demands are identical between the two models, then the extra flow from the reservoir must go somewhere? Do they have a second reservoir or tank for the flow to go into?

 

[jeepeng]

77JQX,

I'm not sure why you are asking, but their system is for 1300 acres and my system lies within their system and I have 155 acres. I did feel it necessary to create their entire model as I'm very close to the same reservoir they are tying to. I mean their first pipe out of the reservoir is at 958 GPM and mine is at 253 GPM.

Does the flow within the system depend on the demand?

Thanks

 

[77JQX]

I'm not sure how to respond. If there's not a second reservoir (or tank) in the model, what else would flow depend on, if not demand?

 

[jeepeng]

77JQX

You are absolutely right! For some reason I was thinking of the system as having an open outflow. My forte is not pressure pipe but rather storm, if you have a straw full of water and your finger is covering the bottom then you have NO FLOW! essentially that's what is wrong with my system, I don't have the same demand as them so I don't have the same flows! Thanks for helping me think through this!

 

[jeepeng]

I have got my model up and running, but I'm still having issues, so if someone could chime in on the following I would appreciate it.

My model is based has a high point and a low point. The low point needs to have PRV'S in place to keep the pressure down. I have 5 prv's in the model all set on 80.

Question Number 1: Is it correct to put the actual pressure you want the PRV set to, or should it be set to an elevation?

Issue #1: the nodes close to the PRV's are at 80, but as I go down the pressure creeps up to 110. This is over 4,500 L.F. and a elevation difference from 5416 to 5360. The PRV is near the 5416 elevation.

Issue #2: only one of my PRV's are opened by the model, all of the others have been closed by the model after I run it. Therefore, I am not getting the flow I think I should be getting because the water is having to come half way around the world to get to the node rather than through the PRV.

I hope that I have been clear and I hope someone can help me.

Thanks Rich