You should really look into getting a rotary hammer. They are quite slick to have. My wife rolled her eyes at the price of them but they go through concrete like a knife through butter. I have the Bosch Bulldog. You will not fear concrete with this tool. Hammer drills are worthless in my opinion, rotary hammer is what you need. I would recommend renting a small rotary hammer and an SDS drill bit by the hour and just drill holes all the way around where you want to work and drill a path of two lines down the middle so you can break the block in half with a sledge and have enough room to pry the concrete out. Wear eye and ear protection. Return rentals once you are done, should only take a half hour to break up what you need. This wont be expensive and will be the easiest way. But, if you want to do this the hard way, as suggested before use a circular saw with a masonry blade and cut the floor where you want to break it up. Caution: lots of dust, concrete dust is real bad stuff, wear good breathing protection and have a shop vac sucking dust and/or run a hose to where your working to make it a wet saw. Plug extension cord for circular saw into GFCI outlet if using wet saw method. Then use standard chisel and sledgehammer.

Thank you very much. The reason I was going to try two traps is the discharge tube that came with the disposal does an immediate 90 deg and discharges downward... which makes it very difficult to connect to the sink drain with enough height to fit the trap. I guess I should buy a straight discharge tube and then I think I can mate it up with the main sink drain using a sanitary tee, if that would be appropriate. I'm trying to improve upon are current design, which clogs frequently. We have the standard white thread-together "sink plumbing" and the disposal discharges horizontally and connects to the sink drain with a 90 deg fitting that has a separation plate in the middle. This is very restrictive. I would like to do it all in black ABS 1-1/2" piping with suitable couplers here and there so it can be disassembled. Regards, Tom

My house is a 1965 vintage. It originally had all cast iron drains but now sort of a mix with pvc. The primary kitchen drain line comes through the basement where the washer/laundry sink are It is 2"ID. The connecting washer drain and laundry sink drain is also 2" ID. You're right about the primary one being too small but that'll never change. I don't know how to post a picture to THS and the fitting's location is pretty much blocked anyway. I went to the Home Depot site to see plumbing fittings. The cast iron primary drain line fitting that I'm talking about looks like an SxSxSxS cross. A little of the washer drain water coming into the laundry sink has always been an irritant but that's as far as it went. Now I've bought a few used kitchen cabinets and a regular kitchen sink to put there. That changes things. My neighbor said to look at a T-valve. I'll check that out. Thanks.

lazypup- Thanks...I always appreciate your knowledge and straightforward answers. I am assuming from what you said that it was intentionally plumbed that way (without a trap) precisely because: 1) that is the way it has to be for a sink to be correctly connected (with one P trap under the bowl), and 2) if someone wanted to hook up a shower or bath to share that drain line with the sink, then there would have to be a P trap at the floor level beneath the shower pan or beneath the tub. Correct? The reason I was thinking the drain line might have a P trap under the slab is that none of my neighbors' houses (identical slab construction to mine) have elevated tubs or shower pans, so I couldn't figure out how that would work. All of our houses have radiant heat lines in the slab, so it's always dicey to be jackhammering out concrete as you might have to do to set a P trap lower under a shower or tub. So I'm curious: What is the minimum height one would typically have to have to fit a P trap under a tub or a shower pan if you don't want to break into the slab? Or is there some other solution to this situation that I'm not aware of?