My wife and I are installing a whirlpool tub. We glued the ABS pipes this weekend and set the tub in place to test out the whirlpool pipes and motor. (We did not mortar it in yet as we wanted to make sure it worked properly.) We used some plumbers putty on the drain and screwed it on. Then we filled the tub to an inch over the jets and started it up. Everything was working great until we drained the tub. Once we started draining the tub we noticed a leak underneath the tub in between the rubber circle piece and the tub (Underneath the tub is the ABS pipe, a rubber circle piece, and then the tub). A bead of water was dripping every two or three seconds from this area. Once the tub was emptied, I tightened the drain a bit more. We filled the tub up with a bit of water. That appeared to fix it, although I did notice a glimmer of water where the beads were dripping out. When we took the tub apart, I noticed that some plumbers putty got in between the bottom of the tub and the rubber circle piece. Was this the culprit? Is the solution to simply apply the putty more carefully next time? Is there a sealant I should use on the ABS pipe, the rubber piece, and the bottom of the tub?

Thanks for your help in advance. This has been a very useful site as this is our first venture into the world of plumbing!