how to input values of bulk reaction rate and wall rate reaction for a chlorine check because whenever i try to input any value it becomes zero automatically

To add to Scott's answer - if you want to use a bulk reaction rate for ALL elements, you would enter this in the Constituent alternative. The "local" bulk and wall reaction rates for each pipe and separate from the global settings - they enable you to override and enter per-pipe values. If you do not have the box checked for "use local", then it will use the global setting.

I would suggest reviewing our training material on constituent modeling such as these:

Introduction to Water Quality modeling

WaterGEMS Advanced Part 9: Water quality modelling

WaterGEMS Advanced Part 10: Workshop 5 (Water quality modelling)

Here is an article that lists other learning resources: Learning Resource Guide for new users of Bentley WaterGEMS and WaterCAD

To add to Scott's answer - if you want to use a bulk reaction rate for ALL elements, you would enter this in the Constituent alternative. The "local" bulk and wall reaction rates for each pipe and separate from the global settings - they enable you to override and enter per-pipe values. If you do not have the box checked for "use local", then it will use the global setting.

I would suggest reviewing our training material on constituent modeling such as these:

Introduction to Water Quality modeling

WaterGEMS Advanced Part 9: Water quality modelling

WaterGEMS Advanced Part 10: Workshop 5 (Water quality modelling)

Here is an article that lists other learning resources: Learning Resource Guide for new users of Bentley WaterGEMS and WaterCAD