Kitchen drain installation

[X_Digger]

8. If it's visible looking down into the drain, it's not likely a washer..

Some bar and 'prep' sinks use a *slightly* smaller trap/basket than is standard, so most universal tailpiece kits come with a bushing that works for those sinks.

Since you've got metal (sink basket) -> plastic tailpiece -> metal (nut), I don't believe you need a washer in there. The plastic will deform to match the basket.

And yeah, hand tight is so vague, with variation in hand strength, as to be next to meaningless. Unfortunately, I don't think there's a torque wrench made for sinks, hehe.