In order to use a Waste King disposal with a Rohl Shaw's sink (or any sink thicker than 3/4" for that matter) you will need to use an ISE flange and an adapter. I just installed mine after trying many different flanges, and finally found this solution: Parts you will need: 1. Extended ISE compatible flange (part #FLG-SSLG) 2. Waste King 3-Bolt Mount Adapter (part #3101) 3. ISE Quick Lock Mounting Flange (part #QLM-00) 4. ISE body flange (part #5298) 5. EZ-Mount Waste King disposal (I used the Waste King L-8000) I ordered all of these parts on amazon. Installation: 1. install the ISE Quick Lock Mounting Flange per the package instructions, except substitute the ISE extended flange. 2. Next assemble the adapter portion -- in order from top to bottom: splash guard (from 3-bolt adapter kit), ISE body flange, adapter (from 3-bolt adapter kit), mount ring (included with disposal). I found it helped to smear a small amount of dish soap between the splash guard and mount ring or else there was too much friction between the two. Press this whole assembly onto the flange installed in step 1 and twist the mount ring to lock into place. 3. Garbage disposal will now twist into place on the mount ring. See my assembled disposal below:

Today must be my day for responding to septic system questions...I responded to one on another forum. Anyway, I do have experience with wastewater treatment and disposal - environmental engineer for about 30 years now. The USEPA has a website dedicated to on-site wastewater treatment, since 1/4 of all US homes have an on-lot system. Here is an excerpt from one of their septic system user guides for homeowners: "Eliminating the use of a garbage disposal can reduce the amount of grease and solids entering the septic tank and possibly clogging the drainfield. A garbage disposal grinds up kitchen scraps, suspends them in water, and sends the mixture to the septic tank. Once in the septic tank, some of the materials are broken down by bacterial action, but most of the grindings have to be pumped out of the tank. Using a garbage disposal frequently can significantly increase the accumulation of sludge and scum in your septic tank, resulting in the need for more frequent pumping." As some have said, you can use a garbage grinder with a septic system - just use it wisely and perhaps you will have to pump out your septic tank more frequently than others. If you perform routine septic system maintenance, that might not even be an inconvenience, since that means you are doing more than the average homeowner with a septic system anyway. This last statement comes from experience, by the way. Here's a link to the EPA pamphlet (in .pdf format): http://www.epa.gov/owm/septic/pubs/homeowner_guide_long.pdf

Thanks Joseph, but I'm actually looking at Blanco Silgranit Sinks. I've been told that the flange that comes with it will ONLY work with InsinkErator.

Kgypso - your contractor is probably thinking of the ol' Badger disposals--he's likely installed a heap of those, and they don't grind very well. I very much hope you are getting disposals (note the plural; I recommend one in each sink) with either 3/4 or 1 hp motor, and all stainless steel innards. If you have that, your disposals will be powerful enough such that grind will be very fine and not clog up your pipes. I just posted another thread about the This Old House Show visiting the InSinkErator factory in Racine, WI. To test the quality of the disposals coming off the line, they had each disposal grind 35 lbs. of steer rib bones and 6 lbs. of pine cubes. Pretty impressive. Furthermore, the InSinkErator rep said that the bones actually help clean the grinding mechanism which makes it more efficient. Make sure your contractor isn't still thinking of the way they used to make disposals 25 years ago, and make sure that he is installing powerful disposals for you (3/4 hp or 1 hp).