SET AUTOMATICALLY A MINIMUM FLOW IN A PIPE

Hello Edgar,

If this is a new system and you are trying to establish a minimum flow in order to ensure pipes are self-cleaning, you can use the Tractive Stress constraints in automated design. This will size the pipes such that the minimum tractive stress is met. See the following article in our wiki:

Tractive Stress (aka Tractive Force, Shear Stress) Calculations and Design

If you need to keep the existing pipe sizes and are trying to input manhole loads based on known flows in pipes, you may be interested to use Flow Monitoring Distribution in LoadBuilder (requires shapefile data for the known flows).

If you need to keep the existing pipe sizes and want to force a minimum flow in all pipes, that seems unusual to me, as you would typically either have measured / metered flow data, or some projection of the loading. If this is the case, could you explain further about the requirements? ("normative in my country")

Hello Jesse and Sushma
The mentioned speaks of identification and placing sanitary charges, but they are manual solutions.
The software allows to automate these steps, which identifies and increases the flow and at the same time subtracts when it exceeds a flow value, because what is wanted is a fictitious flow as established in the standard.

Hello Edwin, exactly that is the problem, I can identify manholes and pipes with a flow less than 1.50 l/s, and fix the issue creating fake flow known, do you know the automatic way to solve this issue. 

I have some questions about the meaning of this 1.5 L/s "normative".

The key in low flow sewer design is that you must provide sufficient tractive stress to move any solid particles and hence have a self-cleaning sewer, which is the goal. Most places don't use tractive stress directly but instead require that you provide a minimum velocity to move solids, usually 0.6 m/s (2 ft/s).  However, this requires hydraulic calculations so most places simply require a minimum slope and hope that the flow is adequate.

At what flow rate must you meet this minimum tractive stress? It appears that in your jurisdiction, someone may have picked 1.5 L/s.

However, did they state the frequency at which you must exceed 1.5 L/s. Must it continuously be above 1.5 L/s, or must exceed this once a day or once a week. What about a system that is not fully built out and only has one house on the upstream most pipes? You should get some interpretation from your regulator who will review your plans.

I personally feel that 1.5 L/s is not a very good value. I live in the first house on the upstream end of a sewer and my house is the only one on that branch. The average flow from my house is on the order of 0.01 L/s. Of course, as you move up the sewer, the  flow is not at the average rate but it comes in pulse every time you run the washing machine, dishwasher, shower or flush a toilet. Those pulses are on the order of 0.3 L/s. I doubt that the flow in sewer in my street has ever reached 1 L/s, yet my sewer works. Most of the time, the flow is 0.0000 L/s.

I would bet that in any system, about 10% of the sewers at the upstream end never reach 1.5 L/s and about 50% only reach it occasionally.

You really need to find the logic behind 1.5 L/s.

It is also best not to talk about :flow rate at a manhole. Manholes can be straight line, Y's, T's, X's with multiple flows. It is best to talk about flow in pipes.

Hi Tom, I agree with you, is not natural to set a flow which doesn't exist, I need to check what is the reason for the 1.50 l/s, but as I wrote before it is because of the rules in my country, I would rather respect the constraints of velocity and tractive stress with the real flow, although it was less than 1.50 l/s.

For now, I solve this problem manually creating fake loads.

Hi Tom, I agree with you, is not natural to set a flow which doesn't exist, I need to check what is the reason for the 1.50 l/s, but as I wrote before it is because of the rules in my country, I would rather respect the constraints of velocity and tractive stress with the real flow, although it was less than 1.50 l/s.

For now, I solve this problem manually creating fake loads.