How do I vent a washing machine without hooking up to a vent stack or through the roof?
You must be asking about a mechanical vent. You can buy these in most hardware stores. They are not acceptable by the plumbing code, but in a pinch they are good. Don't hide them in a wall, in case you need to replace it, keep it accessible. Install it above the highest water level of the washer.
Here is a picture of the mechanical vent you need. Install it after the p-trap coming off a tee. Use a 1 1/2" female pipe adapter to screw it into. Use Teflon tape or dope on the threads. They cost under $5. Here is more info about the vent at Amazon.
Dave(Ask Dave) (About Dave)
Hi, I'm Dave Osborne. With over 50 years experience as a journeyman carpenter, foreman and contractor in heavy construction I enjoyed working with apprentices and sharing the tricks of the trade that others shared with me. Now I get emails from Members all over the world and we include many of my answers in our Free Monthly Newsletters. Some of my answers include drawings and instructions specific to a project, but may also answer your questions. I use correct construction terminology, so you can confidently inform your building supply dealers or contractors exactly what you need.
Membership gives you full access to our hundreds of how-to articles, woodworking plans, converters, calculators and tables. Our Stair Calculator is one of the most popular on the internet. We have projects you can build for (and with) your kids, furniture for your wife, and sheds and gazebos. If you run into a problem or need advice your Membership includes unlimited email questions to me through our Ask Dave quick response button.