We are working on Unidirectional Flushing (UDF) model analysis (early stage of creating the model at this moment).

I have a question after reading your post and the Section 10.9 in *Advanced Water Distribution Modeling and Management.*

Q. 1 K is more accurate than *k*, in the table and we should be using K value for the model analysis, yes?

I guess we could do extensive calculation using the equation 10.15 to find K.

However, the *k value* we calculated using the old hydrant flushing test seemed to use 2.5" hose nozzles instead of 4.5" pumper nozzles.

Q. 2 When one conduct UDF, shouldn't they use pumper nozzles for better flushing? Or, does it depends on the pipe size? Is this something we can find out as we do the model analysis?

Q. 3 What are the common/recommended approach to find the accurate emitter coefficient? If we don't have good data, can we pick a number from the range of K value given for a nozzle size for the first flushing day and adjust it based on the first flushing results?

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Since my question is about emitter coefficient, I hope it is OK to post it here.

Thank you for your advice in advance.

Yoko