To be or not to be Smooth

[Joe Reilly]

More of an observation here.

Drainage lines need to be smooth uniform internal waterways, per IRC, which means those flexible pipes they sell in the stores should not be used...OK I get it.

So then why are dishwasher drain lines rigid and not smooth ?

[John Dirks Jr]

I believe the flex drain pieces are not against the code as long as they are installed in a vertical only position.

The drain tubing that comes with the dishwasher is designed to be flexible for installation purposes and since it's not technically part of the house plumbing piping, it's not a code violation.