Recently I installed a new sink and some new plumbing. On one part of the plumbing I have developed a leak. The leak is where two PVC connections come together, the bottom section has a little rubber washer that goes on top of the bottom section and the top piece screws on. I didn't use any teflon tape on these connections, could that be causing the leak? It's definetly tight enough. I assumed the teflon tape was only for metal to metal connections, not plastic to plastic.