Call a plumber!
ANS 2 -If you mean the water supply pipe for the dishwasher, then it's easy to totally disconnect the copper at the dishwasher connection and at the shutoff valve. Replace it with a flexible rubber, SS braided one. Purpose built for dishwashers to allow easy movement. -Available in HD or ' big box' stores. less than $20
Compression fittings unscrew. Inside you will find an 'olive' (a thin copper ring) which is compressed onto the pipe to create a seal when the outer nut is tightened up. If you wish to replace the compression fitting then you may need to use a junior hacksaw to saw through & remove the olive - be careful not to cut into the pipe unless you wish to replace it too. As for the dishwasher I would guess that you could use the same fitting unless it is leaking. If it is leaking then replace the olive as above.
Yes, plastic pipe, PEX, can replace copper anywhere now.
unscrew it replace it, copper pipe coil easy to replace. Two pipe nuts about 3/8"
Detect the leak and replace that part of the pipe. It is usually better to replace the whole piece of pipe. By removing the junk plastic and replace it with quality piping such as copper DWV or NHCI
Because you will then get a 'galvanic reaction'.
Clean the discharge pipe under the sink where it joins either to the garburator or the drain pipe. Run the dishwasher through a cycle and it should pump the water out thoroughly. Otherwise the pump on your dishwasher is not working properly.
When I have to connect copper to lead "D" I usually solder the copper to the lead or wipe a lead joint depending on the diameter To connect copper to cast iron ,.... If there is a hub I caulk the copper directly into the CI with oakum and poured lead (molten) OR one can solder / braze a female adapter fitting and screw the copper into a CI female fitting
Replace them with copper or plastic pipe.
The pipe has plastic or rubber gaskets in them at the joints. Sometimes they wear out or the pipe gets bumped by moving something under the sink, moving the gasket out of place.
That would depend on lots of factors. When I bought my current home, there was no copper pipe in it, it was all galvanized. Many modern homes have PVC piping in many places. And how many bathrooms are there? How many kitchens? Sinks? Washing machine? Dishwasher? Swimming pool?
100% pure metal is actually quite difficult (some may argue impossible) to achieve. Copper pipe can be produced from one of 5 alloys under the "Standard Specification for Seamless Copper Pipe". They range from being 99.9% pure copper to containing a maximum of 0.04% phosphorus. While in a laboratory it would not be considered pure, in everyday life. . . copper pipe is basically all copper.
Discharge line