My cat keeps having BM in his tent?

You say you don't want to take away your cats TENT. So, do you wash it every week, or after he has a bowel movement in it. That's why he keeps doing it. Don't you think? Replace it. He'll be delighted to have a new little house to hide in; better yet give him a big box, a lot cheaper and the cat won't know the difference. Will he?