P-Trap Problem and Connecting PVC to Cast Iron DWV

[AdrianeS]

I need to install a new P-trap under my kitchen sink and I'm not sure about the proper way to connect it to the old cast-iron DWV pipe. The current setup has a few problems.

1. In the picture you can someone installed a brass adapter so now the galvanized pipe is rusting. I haven't tried to take it apart yet so I'm not sure just how bad it is. I'm not sure what's the best way to go from PVC to cast-iron. I think if the threads are in decent shape when I remove the adapter, I could install a new brass nipple and then use a threaded PVC drain pipe adapter. If the threads are no bad, then install a no-hub coupling.
   
   
2. The other problem is obviously the P-Trap itself. From the adapter is a corrugated/flexible extension tube that slopes down into the trap, then the trap slopes down even farther. I have no idea how to reconfigure this and move the trap up enough to create a proper slope into the vent pipe.

When I searched online, I found a number of different ways to do this and don't know whose advice to follow. I'm hoping someone will chime in and tell me the proper way to do this. Please let me know if more pictures are needed. Thank you!

 

[Reach4]

Compare the altitude of the discharge of the disposal to the pipe going into the wall.

The discharge of the disposal needs to be higher. Could you move the disposal to the left bowl and gain some altitude for the disposal?

If you cannot get the discharge of the disposal higher than the pipe in the wall, opening the wall is called for.

 

[Sponsor]

 

[AdrianeS]

Compare the altitude of the discharge of the disposal to the pipe going into the wall.

The discharge of the disposal needs to be higher. Could you move the disposal to the left bowl and gain some altitude for the disposal?

If you cannot get the discharge of the disposal higher than the pipe in the wall, opening the wall is called for.

I guess it's not apparent in the picture I attached but the outlet from the disposal is a little bit higher than the wall pipe connection. I'd have to measure but it's probably a couple inches. These pictures are a little better:

 

[Reach4]

I guess it's not apparent in the picture I attached but the outlet from the disposal is a little bit higher than the wall pipe connection.

Good deal.
You would want something like this, but you would turn the U of the reversible trap around so that there is more room for the tee at the output of the curved distributor tube. If you want new nut and washer, use something like https://www.homedepot.com/p/Oatey-1...th-Rubber-Reducing-Washers-HDC2698C/316622089 or https://www.homedepot.com/p/Oatey-O...Slip-Joint-Nut-with-Washer-HDC8033C/316622099

For the curved tube, https://www.homedepot.com/p/Oatey-1...-Garbage-Disposal-Tailpiece-HDC2670/316621993 should work. With slip joint, it is ok to mix black and white plastic as well as brass.

I think https://www.homedepot.com/p/Oatey-1-1-2-in-White-Plastic-Sink-Drain-P-Trap-HDC9704B/316622155 is a reversible trap.

Alternatively, use something like you have now, with the straight discharge tube.

 

[AdrianeS]

Thanks for your help! I didn't know anything about reversible traps. I was afraid the only option would be cutting the galvanized pipe which I'm trying to avoid at all costs.

turn the U of the reversible trap around so that there is more room for the tee at the output of the curved distributor tube.

I'm sorry, not quite following what you mean by that. I can see how turning the J-bend around would raise the waste arm up higher to slope towards the vent opening, but what would be the purpose of adding the curved distributor tube? Couldn't I just connect the new trap (reversed) directly to the the tee as it is now? Also, in your picture the sanitary tee changes the flow from vertical to horizontal. I thought they weren't designed to be used in that direction?

 

[Reach4]

The tee in the horizontal middle is usually not recommended by the people I have seen make recommendations as to what is less likely to clog.

That picture in post #4 is not a sanitary tee; it is the end-outlet kind of baffle tee. Your tee is the center-outlet kind of baffle tee . In each case, the baffle is to inhibit input-to-input flow.