I have this washing machine drain line. Please have a look to see anything wrong there? I just learnt that Tee should not be there for the vent. It should be replaced with a wye or combo. But I think it will work well. thanks
It will work.
The reason we started putting in the wye on it's back for the vent was in case someone later on wet vented a fixture with it.
If it's just for venting that fixture, you're fine.
If you do it again, use the combo and the inspector will be happy.
That coupling should be fine assuming it is the correct number for that material, but I wonder WHY he had to use it in the first place. Any competent plumber would have been able to figure out how to make the installation without it.