Where do I snake my standpipe

The standpipe for my washer clogged today. I got a small DIY snake, but it will only go about 4-5 feet into the standpipe where the drain sits.

Pic below is of a cap located to the right of the pipe opening, and near the floor. Do I need to remove this and insert the snake here?

Your hand snake should have gotten through the standpipe trap, on the other hand, it might be too thin to really do anything. That cleanout shout only be touched if you are confident the trap is clear. But if you have to open the cleanout, then your dinky hand snake isn't going to do anything and it's time to call in a drain cleaner.

Got it - thanks Sanjeev.

One more question - why only open the cleanout if I'm certain the trap is clear?

I can get a heftier snake, so just trying to figure out my options.

Because the simplest thing to do is make sure the problem is not in the p-trap...most likely it is not. The cleanout is further down the drain bypassing the ptrap...you will need a larger and longer snake to deal with the main line. Most likely your main is partially clogged.

The reason I say get a professional drain cleaner is because they have the tools and the experience to get it done quickly and with little to no damage. If you do decide to tackle this yourself, you better be very mindful of the plastic threads on your cleanout....your snake can wear down down if you are not careful and then you have a bigger problem because the cap won't thread on and seal properly!

co

If the trap is NOT clear, then opening the cleanout will not do anything to clear the trap or line beteen the trap and the cleanout.

Thanks for the clarification, Sanjeev and hj.