My double sink backed up and I had to remove the pipes under the sink to clear the clog. I put every thing back together but both traps are leaking. I replaced the poly gaskets and lock nuts but still they leak. Any ideas of what I'm doing wrong? Do I need to use any sealant or putty? The kid at Home Depot was no help at all. The pipes are PVC and look to be in good shape. The leak is coming out of the top locknut.

Hey Willie,
It sure sounds like you got that top compression nut cross threaded. The threads are plastic and are easily crossed. Unscrew the nut and check the male threads for any sign of cross threading. Set the nut back squarely on the pipe and try again. No sealant's needed as all the threads do is compress the gasket, however, if you have it crossed the nut will not compress down far enough. Good luck, Tom