20 seems reasonable. I had a roommate who would shower for over an hour. Our bathroom was in our room ( a two room student housing apt so our room was the master bedroom) and she would play music really loud while she showered and it would always wake me up. Sometimes if I got in there before her and accidently left my pj's on the toilet, she would put them on the floor and use them as a bath mat. Ugh. I hated her.