Liquid Liquid Inc /DBA Liquid Design

I thought the installation went very well.  It was quickly done for a reasonable price.  But that was not the end of the story.  About two months after the installation, I noticed water collecting at the bottom of the cabinet under the sink.  It was difficult to determine the source of the leak, so I placed a paper towel under the sink to get a clearer picture.  When next I returned, it was clear the flow was coming from the nut that connected the new pipe leading to the trap and the top of the trap itself.  It was also clear that the flow from the leak was increasing.  Perhaps the nut was overtightened during installation, or perhaps the vibration of the new disposal caused the PVC nut to break, but I can now see a portion of the nut has split.  I have called Liquid Design three times in the past week to determine how to proceed.  All I get is an answering machine, with no response to the messages that I have left.  My initial rating of their work was excellent, but my rating is now downgraded by the problem resulting from the materials used in the installation, and by Liquid Design's non-responsiveness to my requests for follow-up action.