Domestic water routed through stair

I am having trouble finding this in the code manual...

What is the rule for routing domestic water through a stair? Basically I will be branching a 3/4" connection off a main and routed near structure through stair and connect to a roof hydrant above the stair on the roof.

I don't see a problem with that.

I've run quite a few pipes, including fire protection through stairwells.