We just bought a 1980s condo, and there is no p-trap under the kitchen sink. The drain is vertical, and appears to just go down into the slab. I don't know if the previous owner ever experienced any sewer smells, nor have I in the several times I've been in there to work or manage contractors (they haven't complained, either). I can't believe my unit would be the only one that was done that way if it was done incorrectly. Another forum answer suggested that the p-trap could be "underground". I assume they meant in the slab. They also said that if I added a p-trap under the sink, and one already existed underground, it would be bad because I would have problems with the sink draining. Is it common in multiple dwelling buildings for the p-trap to be located somewhere other than right under the kitchen sink? I am going to try to insert a picture of it here. Thanks for any advice. Sorry for the size of the pic. I couldn't quickly see how to swap it out for the smaller one I created.

Remove the clean-out plug and run a snake down until it hits a little back pressure. Remove snake and check to see if end is wet. If wet there is a good possibility there is a trap in the slab. To make water detection easier, add a small piece of clothe to end of snake.

If snake comes back dry I would add a "p" trap under sink.

Chuck

Snaking the drain is a good idea, and so is just unscrewing the plug and looking down into the 2" pipe using a flashlight to see if you can see standing water. If you can see standing water in the pipe you are all set. Otherwise, install a ptrap AND a mechanical vent (referred to as an AAV) under the sink for best drainage!

Mark

You said slab so we know you are on the first floor, are there floors above you? Ask neighbors if you can look under their sink. What you showed us does not look original. I agree, if you don't see standing water in the pipe install an AAV and trap. Did you have a home inspection before you bought, this would not pass a code inspection and you may have recourse with the seller. Also, keep in mind an AAV may not be legal in your location, this may affect future selling of the condo.

In my area, it is general practice to install P-trap for kitchen sink above the slab, inside the cabinet and under the sink.

I may be wrong - but my guess is the original plumber missed the wall with his under-slab rough-in. Pipe ended up inside the cabinet. Happens all the time. Less experienced finish plumber then assumed there is a trap under the slab and connected drain the way it is shown.

Investigate as advised above. If no trap than it is very easy to rework the drain to correct the installation. Come back and one of our Experts will tell you how to put one in.

Question: Do you have sewer smell coming up from the kitchen sink drain ?

Milo