Bottom Line: Your House Your Rules. Does your OCD friend see a Dr.? I am sure there are meds out there to help control it. I think it is great that he feels very comfortable with you, can be himself no matter how annoying to others and not be judged by you. That is a true friend and It just reinforces my belief of what a great guy you are, but for his own sake and safety, he needs to get some guideance with the issue. Where to start....that I do not know. Seems to me OCD is anxiety related, which we all know that takes some professional help.
Maybe when he starts repetitive actions, like the shower thing, you can remind him "You just had a shower" and try to distract his thoughts.
I think the others have advised you well. My motto is to "send the mail to the right address". Talk to the person you are having a problem with and be honest yet not aggressive. I know you will handle this problem well.
Jamiee, My son has OCD. He lives with me. His habits and rituals can be overwhelming. He has a problem with showering too. He can never get clean enough. He has clogged the shower so many times I have had to have the plumber to clear the pipes at least 8 times. I understand the situation. I know you want to be supportive of your friend but this is a disorder that needs professional help. I know there are meds that work to help with the problem. But I think it is necessary to have the counseling as well as the meds. My son cannot take the meds as he has epilepsy and they would interfere with his seizure meds. He has been to counseling, and it helped some but the problem is he didn't like the therapist so it didn't help as much. You, as a friend, and me as a mother cannot cure these people of this disorder. The best suggestion I can give you is for your friend to try to find a counselor who specializes in treating OCD. There are also many books available that explain exactly what OCD is and does offer help. The problem is that as time goes by the condition can get worse and sometimes takes over one's life performing their rituals. It does build up slowly. I didn't realize my son was OCD but I now can pinpoint it to childhood when he always had to take off his shoes at the door and carry them. Over the years different rituals started occuring. I think the best thing to try is talking to your friend. He may very well be aware that he has OCD. Then you may be able to suggest books he can read. I don't know what kind of reading materials you have available but maybe there is something in the library. Don't know if you are able to order from Amazon.com but I got several books that were very helpful. Also, you may be able to find a website if you just type in OCD or Obessive Compulsive Disorder. Sorry to be so wordy, I am hoping my experience may give you some guidance. Best of luck to you and your friend.