Can I drain a dehumidifier in my basement with these?
It looks like a drain on the wall and a toilet drain and possibly a shower but I can’t make out if it has a trap and the placement is a bit strange (if it is for a shower you just need a cap with a threaded hole in either case This would be a good diy project. 

You could add the trap for less than 20$  you might have to cut the cap off I see primer on that pipe in the front so they may be glued. You can purchase the parts at a big box or a plumbing store, save some $ and have a project done on your own. If you only need a threaded cap it might be about 5$ , (small can of glue and the cap)

If you discontinue using the dehumidifier make to seal the trap up or put some cooking oil in there just enough to cover the water it will keep the trap from drying out the oil floats on top even with a trickle going down the drain &amp; oil lasts a long time with out drying out.