Did you ever find out the root reason why your son is/was doing this? I have a 9 year old doing the same and has for years. My husband and I adopted him and his half brother from the foster system and he has done this in prior place,nets but never when he was with his bio mom. He did it a few times, too the point were we could keep up with the smell/stains in our house in California. We moved to Texas 6 months ago and are in an apartment, his room reeks.
Tonight I was standing at the end of the hall telling his older brother to turn out his light when I heard my 9 year old peeing in his room. I ran into his room, saw the wet spot asked him why he did it and he said "did what?" I made him put his hand in the wet spot to make sure it was wet, sure enough it was. I told him t go wash his hands and finish in the toilet.