This column may help you diagnose chronic plumbing problems that you’ve come to live with, not knowing that there was something wrong.

Forty years ago, I used to do home inspections for buyers. The top real estate agents at the time asked for help pointing out defects in existing homes for sale.

I always look at plumbing drain pipes and water lines in every house I’m in. I now use that knowledge to draw plumbing and gas line riser diagrams that help folks get plumbing permits.

Weeks ago, I was in the basement of a house my daughter wanted to buy. The drain pipes and water lines were visible in the unfinished basement. I spotted several significant problems within a minute.

The most glaring defect was a first-floor toilet connection. The vertical drain pipe that connected to the toilet flange connected to a 90-degree fitting. This drain pipe was now horizontal and connected to the main 4-inch drain pipe with a tee fitting. It was lying on its side.

A tee fitting looks just like a capital letter T.…