You took a picture of every thing under there except what you are asking about but the answer is "probably". I say that because the dishwasher has a dedicated sewer connection that could only mean code requirment. The wye is there to prevent water flowing from sewer back into dishwasher in the event of line stoppage. The water will run out on the floor instead.

While not the best photo, it does show the wye. It's all torn apart now, so I cannot take a better photo.

I'm not so sure about it being a code requirement. Our last house, which was in this same town, did not have a standpipe for the dishwasher. The homes are only 1 year apart in age.

If an air gap is required you cannot just stick a drain hose into a standpipe.

The end of the hose is now below the flood level of the standpipe, defeating the purpose of the air gap requirement.

The Y was likely added to lower the flood level of the standpipe to satisfy an AHJ.

Since many places do not require more than a high loop and there does not seem to be any widespread problems in these areas, the air gap requirement has become sort of dumb.

Neither of our homes in this town, nor homes of friends or relatives have an air gap. So, I don't see that as being a code requirement here.

This post was edited by gpraceman on Mon, Jun 10, 13 at 13:58