Does a washer need an air vent to stop m drain overfill?

Your washer should drain to a tub or a stand pipe which is trapped and vented. You are not explaining your situation clearly so this is all I can address. Are you getting back ups or what?

Hi Krut...

I'm not clear here, but if I guess at your issue, I would say that yes, a washing machine drain line needs to have a plumbing vent associated with it, for sure.

However, if the drain is overflowing now but didn't before then most likely the drain line is clogged and needs to be snaked clear... vent or not, right?

Tell me more here. For example, what exactly is happening? How long has it been happening? What material are the drains made of, plastic or metal? And finally, is there a cleanout that is accessible on the drain line in question... ;)

Back to you...

Mark

Hi Bob (ballengerb1)...was writing as you posted! I see we are on the same page, for sure!