Importance of Unit Headloss vs Friction

[DRC WASH PM]

I'm modelling a rehabilitated water system in DR Congo. I'm currently working out the new pipe needed for the system trying to ensure a residual Pressures between 10-30m and a Velocities between 0.5-2m/s (during peak flow). I also want to keep the headloss less than 5m/km, however for many of the pipes increasing the size to ensure a headloss less than 5m/km the resulting velocity is less than 0.5 m/s and the system becomes significantly more costly due to the larger pipe necessary.

How important is maintaining low headlosses in a system (in particular when reducing the headloss will significantly increase the cost of system and the residual pressures and velcocities are acceptable with the current sizing)?

The attached model is not very systematic due to the location of the existing tapstands and pipe. Tank 67 is a new tank and is connected directly to the newer tapstands in the town, as the existing pipe is too small and there are many private connections and leak (hence the duplication of the pipeline in the denser area). In addition, the model is currently unbalanced (I think this is due to the demand being higher than the supply - also trying to resolve this)

[Daniel Antonio Colocho Arévalo]

Think about this:

The velocity is only a parameter to avoid sedimentation in the pipe system, is nos a parmeter that the users can observe and toay ¡The elocity in this system is not adecuate!, the users can say about the pressure in the domiciliar conection.

In other hand, if your system has  treatment units and the turbidity is so low, ¿wath about the velocity?.

Analize the permanency of water in the system, this can serrve you more than velocity.

2013/7/1 DRC WASH PM <tth...@gmail.com>

I'm modelling a rehabilitated water system in DR Congo. I'm currently working out the new pipe needed for the system trying to ensure a residual Pressures between 10-30m and a Velocities between 0.5-2m/s (during peak flow). I also want to keep the headloss less than 5m/km, however for many of the pipes increasing the size to ensure a headloss less than 5m/km the resulting velocity is less than 0.5 m/s and the system becomes significantly more costly due to the larger pipe necessary.

How important is maintaining low headlosses in a system (in particular when reducing the headloss will significantly increase the cost of system and the residual pressures and velcocities are acceptable with the current sizing)?

The attached model is not very systematic due to the location of the existing tapstands and pipe. Tank 67 is a new tank and is connected directly to the newer tapstands in the town, as the existing pipe is too small and there are many private connections and leak (hence the duplication of the pipeline in the denser area). In addition, the model is currently unbalanced (I think this is due to the demand being higher than the supply - also trying to resolve this)

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Atte.

    Ing. Daniel Colocho
danco...@gmail.com

Paz y bendiciones a usted y su familia.

 

La forma en que jamás DIOS rechazará nuestra presencia es presentándonos humillados a lo sumo y humildes, reconociendo que sin DIOS valemos menos que la nada y que lo que nos da valor para ser merecedores de su amor es que fuimos redimidos por el Redentor Amado. (Sal 51:17 y  62:9)

 

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[Santiago Arnalich]

Hi,

Unit headloss is only an indicator of how efficient are your pipes, thus:

- It becomes important if you pump (spend money to overcome pipe resistance is usually not very smart), the area is very flat or to check that the system is not being chocked at any point.

- If you have a gravity system and big slopes, you may want to install very inefficient pipes in some areas.

Velocity is only important if the water in your system has particles that can sediment and in any case you can open the washout valves that you should install in low points to clean the pipe periodically.

Page 124 and on of this book describe calculation criteria

Santiago Arnalich
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