Hi, I have a 3" sewage pipe that runs from the basement floor to the roof. I cut about a foot of the sewage pipe and connected a 2" pvc pipe with 2" trap for the washer drain line.
I am getting over flow from the stand pipe. There is no blockage of the sewage pipe. When I cut it open, it was clear and clean. Above the basement there is only a sink that shares that sewage line. My question is do I need to add an air vent(line)? Should I use a compressor where the washer line meets the stand pipe and get rid of the trap to improve water flow? Attach is a diagram of the plumbing. Please Help. Thanks you so much.

Tom

Your attachment didn't make it. How high did you make your stand pipe? Do you have a new Maytag washer? If the stand pipe's 36" or longer then perhaps you need to install a compression fitting, (See image) and make it a closed system. I've had one for years with no bad effects. Good luck, Tom

I did not see your attachment but did you understand that you tapped into the vent stack, not a sewage pipe? You have created a wet vent and I suspect it isn't clean as you think donw at the floor level. Rod it out, the 2" pipe should handle nearly all washer, maybe not Maytag.

I checked and the kitchen sink upstairs water is flowing down this sewage pipe. I tried the compression fitting and it worked. Somehow it slowed down the water flow and even prevent the water from flowing up the stand pipe. I used to be able to hear the water rise up the stand pipe and the stand pipe would get heavy but now it doesn't. Thanks so much for your help.