New Drain is Slow?

May or may not have an issue with a new laundry drain line that was installed. The drain line is 2" all the way to a nearby existing vent. I tested the water supply line (3/4" down to 1/2" right before values) before drywall install and the drain is not able to keep up with the amount of water that the 3/4" can deliver and the drain will overflow if the water supply is valve is fully open. If I close the valve halfway, it works ok.

It may not be an issue depending on how much water the washing machine pumps out, however I first want to make sure there isn't something obviously wrong with the plumbing. See attached images. Any help is greatly appreciated!

Is that a rubber neoprene/rubber santee you have there connecting the trap arm to the exiting vent.

Good luck with that.

Mr_David said:

Is that a rubber neoprene/rubber santee you have there connecting the trap arm to the exiting vent.

Good luck with that.

Click to expand...

Yes, it is. It connects the larger cast iron pipe that goes below to the crawl space to the PVC pipe that vents up to the roof. Its my understanding I have to use a neoprene connection coupler to connect the cast iron to pvc anyway. If there is a specific issue, I can be sure to replace it.

torquewrench said:

Yes, it is. It connects the larger cast iron pipe that goes below to the crawl space to the PVC pipe that vents up to the roof. Its my understanding I have to use a neoprene connection coupler to connect the cast iron to pvc anyway. If there is a specific issue, I can be sure to replace it.

Click to expand...

You can not use "neoprene" Fernco type fittings above ground and no inspector I have worked with would ever pass a rubber tee. The rubber tee has to be replaced with hard pipe (I prefer PVC) and attached to the existing cast iron with a stainless steel shielded banded coupling. The chances are high the rubber tee will fail in your wall and lead to horrible problems. Replace it.

As to the drain overflowing, the piping looks OK. You used 2" right? You must have a partially clogged line.