Wisconsin house is circa 1950 and built on-slab, no basement or crawl space. Utility room has floor sink roughly 18" diameter sunk down into slab. Top portion of floor sink is cylindrical, then a conic section, then cylindrical drain pipe at bottom, roughly 4" diameter. A 4" pipe is pushed at an angle into the drain pipe and extends upward, acting as a drain stack for the washing machine. There is a laundry sink with a 2" drain pipe, including a P-trap, which goes down adjacent to the "stack" pipe. I do not see a vent line. I believe there is a trap at the bottom of the floor sink drain, under the slab, because there is no sewer gas smell. The slab is 5" to 6" thick. Per a clean-out about 30 feet from the floor sink, the drain line is cast iron and is 3 to 4 feet below the slab.
We will be adding a kitchen sink and dishwasher about 20 feet from the floor sink. It makes sense to attach to the sanitary drain system at the floor sink, because the location of the line is known there. However, I'd rather not cut up the concrete slab and dig down 3 or 4 feet with shoring and so forth to avoid undermining the rest of the slab. We would saw a channel into the slab top deep enough to carry a 2" drain line and 2" vent line, plus PEX hot & cold feeds.
Is there any way I can drain the kitchen sink and dishwasher into the floor sink? For example, I could add a gasketed cover and convert the floor sink to a sealed "crock", with a bottom drain instead of a lift pump. This would require adding a vent, I assume. I might use an AAV (Studor vent) at the kitchen sink if I can't get a vent line routed to the roof or outside wall. I don't know if an AAV is an option for the sealed floor sink.
I'm also curious why residential sinks can't use indirect piping while commercial (restaurant and bar) sinks and dishwashers require the air gap. And why indirect piping is limited to relatively short distances.
Thank you in advance for your input.
We will be adding a kitchen sink and dishwasher about 20 feet from the floor sink. It makes sense to attach to the sanitary drain system at the floor sink, because the location of the line is known there. However, I'd rather not cut up the concrete slab and dig down 3 or 4 feet with shoring and so forth to avoid undermining the rest of the slab. We would saw a channel into the slab top deep enough to carry a 2" drain line and 2" vent line, plus PEX hot & cold feeds.
Is there any way I can drain the kitchen sink and dishwasher into the floor sink? For example, I could add a gasketed cover and convert the floor sink to a sealed "crock", with a bottom drain instead of a lift pump. This would require adding a vent, I assume. I might use an AAV (Studor vent) at the kitchen sink if I can't get a vent line routed to the roof or outside wall. I don't know if an AAV is an option for the sealed floor sink.
I'm also curious why residential sinks can't use indirect piping while commercial (restaurant and bar) sinks and dishwashers require the air gap. And why indirect piping is limited to relatively short distances.
Thank you in advance for your input.
