So recently when I was in a toilet, I noticed a strange behavior of the water that flowed down a nearly vertical pipe of my friend house. Instead of flowing straight down on the nearly vertical pipe, the water swirled around the pipe and it flabbergasted me. The pipe is made of some plastic or rubber I don't know but I need an explanation of why the water behaved such way, why it didn't just flowed down the pipe in straight flow. I'm sorry for my bad writing and explaination. English is not my mother tounge here is a photo of the strange behavior of the water (pls excuse the bad quality of this photo). So the clear visible line was the water flow. Notice how it just swirled around the pipe. May I know if water surface tension has anything to do with this ?
I'm sorry if my question sounds silly. I'm not an expert in this field but rather just a student from a standard high School.