Kitchen Sink - Two Waste Lines

[J_Bert]

Good Day,

First off, thanks for the forum. I have used other peoples posts regularly to help around my new home and think you all have a great community here.

I have an issue under my kitchen sink and after reading other posts, it seems that I need to post some pictures. I have two waste lines and a third capped off line. I want to cap off the other waste line, but want to make sure I am not causing any issues down the road. Here are the pictures. Please let me know if you have any questions or need a better angle and thanks for the help.

 

[CountryBumkin]

IMO - It looks like the unused (black) drain pipe was connected to the dishwasher drain (which is now connected to the garbage disposal). So you could cap this off. Do you have two dishwashers (I see a Y-fitting with a two drain lines ( a grey and a black). Where does the gray flex line go?
I would guess there was a dual sink there, each with its own drain connection at some point. The white PVC line with the cap is the cleanout. You need this have this cleanout - so leave it as is.

 

[Sponsor]

 

[J_Bert]

IMO - It looks like the unused (black) drain pipe was...

Thanks for the response. The gray flex line is indeed the drain for the dishwasher and is now connected to what looks like a newer disposal. I assumed the same things as you. The dishwasher used to go to it and it could have been for a double sink in a previous life, yada yada, but I am glad to hear that at least two people think the same thing (The "plumbing guy" at Ace agreed as well.).

I ended up buying a 2 in. cap for the outside of the 1.5 inch pipe. I plan to remove the p-trap and just cap it at the end of the downward facing elbow. I just want to know if there are any potential pitfalls before capping it or a right and wrong way to cap it.

Plan, for now, is:
Remove P-trap
Apply silicone tape
Screw on 2 in. cap

 

[CountryBumkin]

I don't think you will find a screw on cap that will fit the p-trap piping.
You could unscrew the barb fitting from the white reducer piece and put a PVC threaded plug in it.


EDIT: explanation - I think (thought) those under sink P-traps used a "straight thread" with tapered sealing ring and a screw-on collar to tighten it all together.
Looks like it worked for you. great!

 

[J_Bert]

So, I found a cap that fit the end. It was a 2" PVC cap. Here is a photo.
Note: The liquid in the p-trap was the most horrible smell and I ended up putting latex/silicone around the fitting to make sure it was watertight.

 

[Kreemoweet]

So what's up with the dishwasher air gap? That's the blue thing in your 1st photo that the DW drain connects to. It looks like
someone has just shoved the air gap body under the sink/countertop level. How is it not leaking? DW airgaps are required in
Wash. state, and the top/cap to that thing is supposed to be sitting on top of the sink/counter above the sink flood level. It is serving
no purpose where it is now, might as well just connect yer DW drain line directly to the disposer.

 

[J_Bert]

So what's up with the dishwasher air gap? That's the blue thing in your 1st photo...

We recently bought this house and the last owner did not do anything to the house as far as improvements and basically just did the bare minimum. Given my experience with other parts of the house. I'm guessing that she wanted a new sink, but didn't want to have to drill a hole in it for the air gap and she also didn't want to have to buy a longer hose to get it from the sink level to the disposal. She also replaced the disposal, but used the old rusted snap ring instead of installing the new one. Probably because it fit and it was there already.

Thanks for pointing it out in case I wasn't aware. I really do appreciate it. Luckily, we don't use the dishwasher anyway, so it is on the list, but not on the top. Next on the list is reducing the load on a few of the breakers in the house and getting about 15 small stumps ground up that line the property, again she cut the trees down and left all the stumps...