Basement drain pipe run in line with main pipe

[InedibleShultz]

Howdy all!
I've got a bit of an unusual setup in the basement i just want a sanity check on. At some point a previous owner ran a new main lateral pipe above the floor. Looks to have been professionally done & have had no problems with it as is.
However, they did plumb in a drain line (for a potential sink) that runs right alongside the main lateral for about 4 feet. Picture shows the setup.

It's currently blocked off, but we're looking at putting in the sink it's intended for. As far as i can tell by eyeballing it, the centerline of the drain stays just above the centerline of the main. My question is simply whether this is good enough, or if the drain pipe should be elevated more.
Obviously if the sewer backs up we're gonna have a bad time, but should it be fine under normal conditions?
I noticed the p trap for the washing machine is above the main line completely. Should i make sure the p trap for the sink is as well?
Thanks in advance for any advice!

 

[MicEd69]

What are all the lines shown in your picture servicing?

The line coming from the right side of the picture appears to be draining something, correct?

Yes, the P-trap for the sink should be above the branch line to which you are connecting.

It is better to enter a line from above like that 2" wye going into the 2" line running parallel with that 3" branch line. But with that 2" coming from the right and your new sink, you should be fine. Make sure all your fixtures are properly vented.

 

[InedibleShultz]

What are all the lines shown in your picture servicing?

The line coming from the right side of the picture appears to be draining something, correct?

Yes, the P-trap for the sink should be above the branch line to which you are connecting.

It is better to enter a line from above like that 2" wye going into the 2" line running parallel with that 3" branch line. But with that 2" coming from the right and your new sink, you should be fine. Make sure all your fixtures are properly vented.

The pipe coming in from the right is the washing machine drain. The pipe going straight up is a vent. The pipe straight to the left is the one for the sink that's blocked off. Everything else in the house is connected to the big main pipe further upstream (to the left).

 

[MicEd69]

As I said above, it is better to enter a sewer line from above or at a 45-degree angle, but your washing machine is entering that 3" line from the side now, so you will be "washing" that line every time you use the washing machine (LOL) as well as when you use the new sink. You will need to vent the sink's P-trap separately even if it is close to the washing machine wye. It cannot be wet vented through that line as there is a horizontal run over that 3" branch line.