how much math do you need to know to be a plumber?

At that stage in life where college just is not going to work out anymore. I would like to learn a trade such as plumbing. My main concern is I am not at all strong in math. Yes, I can add, subtract, divide, and multiply. I can also do fractions. Is anything else needed? Or are there any other lucrative trades that a high level of math is not required.