My house was built in 1972. I moved here about 6 years ago and noticed that previous owners drilled holes in the exterior clean out lid for the washing machine drain. When the washing machine drains, it backs up and spews out the cleanout instead of flooding the house. I finally took a snake today and sent that sucker about 28 ft down the pipe before it wanted to fold on itself.

Could my pipe just be undersized? I don't think I ever felt anything that would give me reason to believe it's clogged, unless it was 28 ft down the line.

I would run a camera down it to find out. Do they rent those?

We previously had a house in Cedar Hill built also in 1972. I believe code was different then and the interior drains were I think were 1 1/2” instead of 2”. This is from memory only so may not be 100% correct. We would periodically have to have a plumber come out and clean all the drains and all vent stacks or we would have some backup issues. It was never completely blocked but just enough to cased a lot of gurgling noises from the drain backing up.

vent stack could be stopped up, look at the roof where the washer is and see if there is about a 1 1/2" pipe sticking up in the area.

when you ran the snake did you feel any 90* turns, hard to get it to pass anywhere?

It's possible the vent isn't completely clear. I never felt anything that seemed like a 90 degree bend. It went in pretty smoothly for most of the length, maybe at 20' it gained resistance but I figured it was just from trying to push that far.

20' may have been the tie in to the main line.

Run a water hose down the drain and see if it backs up. If it doesn't, I would look into upsizing the washer box to 2". The newer washing machines dumps a higher volume of water at once and the drain cannot keep up. If it backs up with a water hose then I would say there is an obstruction in the line.

I have a 50' run from washing machine to the tee that connects to the main drain. When I was younger we had a family friend that was a plumber. I called him and described my house. He said he knew exactly where the problem is and it is that tee. When mine gets clogged I rent a 75' or 100' powered snake. I was out of town the first time it got clogged and the wife described a fountain coming out of the kitchen sink when the washer hit drain cycle. Fortunately most of the water ran out the garage. Instead of drilling holes in the cleanout cap I have a pipe with a screen on one end and a threaded elbow on the other that I use for an overflow. I hook it up when I suspect things are draining slow. I never use the disposal and use a strainer on kitchen sink.

It's the only location that I know that backs up. I may try to get ahold of a camera.

When those high volume pumps first came out on washing machines there was all kind of hell if you had the old 1-1/2” or whatever it was drain plumbing. The drilled holes and screened elbows are a crafty solution. Mine never got that far and I had to up size my drain piping in the house but mine was much older pier and beam. That was really fun. Not.
If your’s has been working, I bet a powered roto-rooter and a good clean out of your vents would fix it.

It's never worked properly, which makes me wonder if it's a sizing deal and has been this way a long time.

Biggest snake coil I would use is a 1/2" with a single cutter, at least the first time. Pull that out and put on a drop head. Go slow and run a tiny bit of water when you do. Should be a 1-1/2" pipe to the main sewer line of the house. SHOULD being the key word. If it gets hung while retrieving it, walk away for a few minutes and do NOT force it. We've broken a coil or two doing that and that is a major issue.