Clean out line or pre-plumbed drain

[Doom]

I am trying to add a sink to my laundry room. I have a washer draining into a standpipe in my laundry room. 2ft from the standpipe is a PVC plug on the wall (~36" off the ground). I figure this a drain clean out line. ~6ft from the standpipe is a second PVC plug on the wall (roughly 12 inches off the ground). What is an easy way to figure out whether this is a drain for a laundry sink?

 

[hj]

Th one closest to the standpipe would normally be its drain, but otherwise remove the plugs and run water down the standpipe.

 

[Sponsor]

 

[Doom]

I am looking to install a sink in the room. If the plug by the standpipe is it's drain clean out plug (36" off ground) I can't use it for the sink. Right? I am hoping that tge other plug was a pre plumbed drain line for a sink. What else would the 2nd plug be for? Any help is greatly appreciated! I have not taken any Sheetrock off the wall yet and hope not too, if possible. Thank you

 

[Smooky]

Is it in a basement or down stairs? Is there plumbing above this area?

You could take the plug out. Take a section of cloth or something similar and put it in the pipe with a tail hanging out. Put the plug back in and screw it in a little to hold the cloth in place. Go run all water using fixtures above this pipe. If it is a drain for something above the end of cloth in the pipe will get wet.
If the stand pipe has a p-trap below the floor then the pipe with the plug could be the vent for the washer drain. If that is the case there are several ways to do it.

A picture might be helpful. A little more info would help too.

 

[hj]

IT would be allmost unheard of for a "future" drain connection to have a plug in it, (it would make the connection more difficult). More likely it is a cleanout for a separate drain.