Originally Posted by
Milo Dolezal
I would never recommend to cover up clean out. It is there for a reason. People pay lots of money to have new Clean Out installed. One day you will need it and you will be breaking up the concrete...
You can pour concrete to cover up the hole in the ground but you should cut off clean out extension level with the ground. If it is in busy area, you have to cover it with flat, cast bronze cover.
Moreover, wing nut is not proper way of covering clean out outlet. It is for rough-in test purposes only. You can buy Female adapter and flat screw-in plug for ABS / PVC pipe, or if it is Cast Iron get Blind End and attach it with No-Hub coupling.