Some inferior codes do allow for the use of a 11/2" kitchen waste line as these codes normally serve bottom of the line housing and areas where there is a lack of code officials looking to protect the home owners.

The 11/2" waste is ok for bottom of the line housing like tract houses or where builders require plumbers to go as low as possible on pricing and price not quality is the driving force.

Personally I never used anything less then a 2" waste line as I feel most folks may one day install a dishwasher and or a garbage disposal and rather then having the waste back up into the sink and drain slowly I would rather make sure the waste is carried away as fast as it enters the drainage system.

I also would never install an AAV unless I was out to punish the home owner.

With food particles entering this waste piping why use bottom line sizing?

Also think seriously about using longer radius drainage fittings so you will have less of a possibility of future stoppages.

Thanks for the information on the waste pipe size. One more question...when bringing in the waste pipe is there a standard height that I should bring it out of the wall? Would I be better off bring it up thru the floor ? And ,if so, should it be center of sink or offset a little for less trouble in getting the trap in?

The reason I was going to use 1 1/2" for the waste is because I have a cast iron fitting cemented into the basement floor with a 1 1/2" galvanized pipe leaded into its hub. Is there a way to chop out the lead and increase the pipe size to 2" without changing the cast iron fitting?

Normally unground piping is a min of 2" for waste and the lead in the hub I usually burn out carefully and then caulk in the new piping as needed. Are you sure the pipe in the hub is only 11/2" and not 2" ??

If it is 2" you might consider cutting the existing galv pipe about 2" or 3" above the hub and use a NO HUB coupling NOT FERNCO and then go no hub cast iron.

The trap I try to install between 10" - 12"

above the floor as this way I have room to turn it on the nipple yet have plenty of height if I decide to install a garbage disposal at a later date or I need to install a washing machine tee on the trap inlet so no suds can rise into the sink

I also do not like to place the trap under the floor if possible in case I have to have access to snake it or change an offset ot add another fitting

The diameter of the plumbing from the Main sink IS 1 1/2" which then connects to 2" waste pipe. Bob Villa or not - to suggest 1 1/2 is only found in 'bottom of the line' housing is inexcusable for a man supposedly in the know!
'Code officials' ???? So.....the 'inspections' when you buy and sell a home must either be incompetent or dishonest.

The under the sink plumbing attached to your sinks Main and Food preparation sink (preparation line will invariably have a disposal unit) is 1 1/2 inches.

I dont see a problem with going with a 1 1/2''pipe. Personally i would go a little bigger but worst case scenario there are plenty of affordable options to clean out your drain if it fills up. Things like drano were made for instances like these.