Remodeled Kitchen Sink Plumbing

I am in the midst of installing my new kitchen in an apartment building constructed in 1969 in Canada. I intend to use an under mount sink in my new design but only really recently realized that my drain pipe was roughed in at 25-1/4 inches from the finished floor (middle of drain pipe). The top of my sink cabinet (minus countertop) is 34- 3/4", meaning I have 9-1/2" to work with. I have no intention of installing a Garborator.

I've spoken with 3 plumbers now as well as some big box store "experts" and I've yet to receive any kind of consensus from them about what I can do. I am trying to avoid removing the wall and cutting into the cast iron pipe in the wall and lowering my drain.

It has been recommended that I utilize my clean out to create my new drain but it seems that the threads on the inside of my pipe are not compatible with the male adapter I purchased.

I'm wondering if there is a minimum amount of space one needs between the drain and the bottom of the sink. If I were to configure a long trap out of 90 degree bends would I be able to use an 8" depth sink? I realize that if I were to do this I'd see water almost flush with the top of my tail piece but are there other consequences of this?

I appreciate any and all suggestions!

It always best to know what sink is being used when the plumbing is roughed in. Most new installs here put the trap adapter 15-16" above the floor.
If the piping in the wall is vertical, you only need a hole wide enough in the back of the cabinet to cut out the old tee and install a new one. A new false back in the sink base hides it when the job is done.

cacher_chick said:

It always best to know what sink is being used when the plumbing is roughed in. Most new installs here put the trap adapter 15-16" above the floor.
If the piping in the wall is vertical, you only need a hole wide enough in the back of the cabinet to cut out the old tee and install a new one. A new false back in the sink base hides it when the job is done.

Click to expand...

Thanks for your suggestion. The pipe in the wall is verticle so what you suggest would be possible but I'm confused as to why everyone else I've spoken to has told me that if I wish to lower my drain, then I have to cut out a 1.5 foot section of the cast iron pipe and replace it with a new piece with a lower drain. This process is obviously something I'm trying to avoid as I have 4 apartments above me and I'd have to have them suspend their water use while the work is underway. Is your suggestion viable for a cast iron pipe?

The pipe should not have any waste coming down from the floors above, as it is a vent. The concern with cutting in a new tee is the weight of the pipe above, and how it is supported.
In most areas it is illegal for an unlicensed person perform plumbing work in a multi-family residence. The liability you take on in doing work like this is substantial.

The problem with trying to make the current drain opening work is that water would "fill" the disposer. When you turned it on, it would make a horrendous vibrating sound until it pumped the water out. In addition, the water standing in the unit would cause it to deteriorate very quickly. The cleanout has a "test plug" in it, so the threads may be rusted out, but it is also a 2" opening, which is why your fitting does not work in it.

You may want to open the wall and see what can be changed there. If there is any way to lower the drain, or if not, get a shallower sink.
First rule of plumbing is that water goes "downhill".

9" from the center of the drain to the top of the cabinets, which is where the sink rim will be, will be very tight for any sink and drain combination and absolutely impossible with a disposer unit.