I'm installing a new tub in my bathroom that has a spring pop-up drain that uses metal linkages. Can I use a PVC tailpiece instead of the brass one supplied with the kit? Or is there a danger in having metal linkages inside the PVC?
I would stay with the kit. Brass will probably out last PVC. If the linkage rubs on the PVC during use, it could eventually wear a hole through the pipe. Only my opinion, not from experience.
I can't envision the kit you're referencing. Got a model number? I know the old Kohler Clearflo is a brass kit that is specific to several kohler tubs.. I can't think of a reason why plastic wouldn't work as long as its schedule 40 PVC/ABS and definately NOT tubular plastic. But.. not really sure which drain you're working with..
Manufacture won't stand behind your modifications if that's of any importance to you.
Personally I like to install a cable drive or a clicker style drain because they have the least amount of parts to create clogs.