You could also look into becoming an electrician. That touches on more high tech stuff than plumbing. And you get to flex your math skills as a master electrician. I think (hope) that there is a fairly rigorous certification for getting into electrical apprenticeship programs in every region. In the city where I grew up, they had to sit for exams in order to get to specific levels.

Edit to add: while both jobs have too much crawling through spiderwebs in crawlspaces for my tastes, electricians encounter orders of magnitude less poop than plumbers.