I need to slightly move my existing sink waste to marry it up to my new sink.I'm going to need to use some plastic piping and some plastic joints.Do i need to use a sealant on the joints even though they have a rubber washer inside the rim or do they just push fit.If I need to use a sealant what is the best type? I think i may also need to seal around the plug,can anyone recommend what to use.All replies much appreciated as girlfriend is now threatening to kick me out if I don't get the sink sorted out sharpish.