How to lower a drain arm
I am installing a new kitchen sink with a garbage disposal, but it turns out that the existing drain is too high, and I need to lower the drain arm so that the disposal unit does not fill with water. I think this is something I should be able to do myself, rather than hire a plumber, although I have not done anything like this before. I am looking for tips on how I should proceed - how to cut the existing pipes, what kind of 'T' fitting I need to get, and how I should do the installation. Any help would be greatly appreciated. Here is a photo showing the drain/vent pipe and the existing 'arm'. I should add that the new arm can be shorter, so that it will end up to the right of the water pipes, so there is no interference to worry about. Also, what would you do about the framing - it looks like I will need to cut a new notch below the existing one, but if there is some way to avoid cutting through the wood that would be great.