Review on High-Quality Oatey 39012 1.5 in. NPT ABS in-Line Vent in Black - Ultimate Plumbing Solution! by Michael Hale

Our washing machine has an unpredictable drain overflow from time to time. First I made sure the drain hose couldn't pop out of the drain pipe. That seemed to work for a while. But then it started again. I knew the sink needed proper ventilation to function. One was already installed on the drainpipes, but it looked very old and I couldn't tell if it was still working. I looked online and there were more expensive replacement parts out there and I couldn't even find that type. I thought they might not be made anymore. I'm thankful I finally found it, although the size in the advert is wrong, it's for 2 inches. A simple swap and the problem was solved.