Reddit reviews Simer 2925B Self-Contained Above-Floor Corrosion-Resistant Sump/Laundry Sink Pump, 1/4 HP, 115V, 1-1/2" Discharge Pipe, Handles Solids Upto 1/8", 6 Gallon Drainage Tank, Black
We found 3 Reddit comments about Simer 2925B Self-Contained Above-Floor Corrosion-Resistant Sump/Laundry Sink Pump, 1/4 HP, 115V, 1-1/2" Discharge Pipe, Handles Solids Upto 1/8", 6 Gallon Drainage Tank, Black. Here are the top ones, ranked by their Reddit score.
Compact contained sump pumpEasy under-sink installation1-1/2" Discharge pipe sizeHandles solids up to 1/8"horsepower is 1/4 HP
You need to use a Laundry Pump to get the water from the machine up to the sewer line.
They way they have it set up now it not up to code, it putting unnecessary strain on the washing machine pump, and water will run back down into the machine. Adding a sink is not necessary as the correct type of pump will do the job. Water pumps from the machine into the laundry pump which then pumps it up into the sewer line.
The pump I linked is only one example.
Someone posted this yesterday.
https://www.reddit.com/r/HomeImprovement/comments/6zr3l2/awful_washer_install_how_do_i_fix/
The fix was a laundry pump
Credit to /u/drefen
https://www.amazon.com/Simer-2925B-Sump-Laundry-Sink/dp/B00296QCJ6/ref=sr_1_6?ie=UTF8&qid=1505263592&sr=8-6&keywords=laundry+pump
Another option you might consider would be something like this and then tie it into an existing drain.