Pipe Material Selection for Draining Pipe of Clarifier

Hi everyone.

This is my first time posting in this forum :o:o:o. As we are replacing our draining pipe for our hopper bottom type clarifiers (14 units), I would like to ask for some advice regarding the material selection of the pipe.

For the plant, we are dosing max 7.3 mg/l pre-chlorine. The quality of the water is sometimes mixed with sand. The reason we are replacing the pipes is because the condition of the pipes have deteriorated very badly (20 years old). Sometimes the draining pipes are also clogged.

As for the pipe material, I'm inclined towards selecting SS316 as this material would negate the effect of the chlorine in the water. However, the cost for SS316 is more expansive than SS304, mild steel or cast iron. Can I select PVC for the draining pipe as PVC would be cheaper and not be affected by chlorine? Or there would be an issue with the installation of the PVC for the draining pipe?

For bigger picture, below is the drawing of the clarifier. Thanks.

[IMG]https://www.engineersedge.com/engineering-forum/attachment.php?attachmentid=2018&stc=1[/IMG]

Look at PVDF