Nobody walks into the plumbing aisle on purpose

It's 7:40 on a Saturday and the plumbing aisle smells like PVC primer and rubber washers. Nobody here's browsing. Every man in this aisle has a towel on his kitchen floor at home and a part in a zip-top bag in his hand. I'm one of them. I came in for a toilet flapper, and I've already been standing in front of the wrong wall of flappers for six minutes. The guy in the orange apron has seen me. He's waiting to see if I'll ask. I won't. Not yet.

Heard in the aisle

"I didn't turn the water off. It's just a faucet."

The real lesson: Close both shutoff valves under the sink, then open the faucet to bleed off the pressure before you loosen anything. If those little valves won't budge, or you don't know where your main shutoff is, go find it today, while nothing's spraying.

"Do you have the bendy thing? It goes from the wall to the other thing. It's about yay long."

The real lesson: That's a supply line, and they come in different lengths and connection sizes. Faucet lines usually have a 3/8-inch compression end at the valve, and toilet lines run 3/8-inch compression to a 7/8-inch fill-valve connection. Buy braided stainless, and bring the old one so you can match it on the spot.

"Lefty loosey. Unless I'm on my back under the sink. Then I honestly don't know anymore."

The real lesson: The rule only works when you picture the nut head-on, from the side the threads are going into. Lying on your back and looking up flips it in your brain. Picture yourself looking straight at the nut, then turn.

"I wrapped the tape, threaded it on, and the tape came out the other side like a party streamer."

The real lesson: Look at the open end of the male threads and wrap the thread tape clockwise, the same direction the fitting tightens, three or four wraps. And skip the tape entirely on compression fittings. The ferrule makes that seal, not the threads.

"It was leaking, so I tightened it. Then I gave it one more for luck. Now it leaks worse and it's making a noise."

The real lesson: Overtightening cracks plastic nuts and crushes compression ferrules. Plastic slip nuts on a P-trap go hand-tight. Compression nuts go hand-tight plus about a quarter to a half turn with a wrench. Then check for drips and snug a little more only if you need to.

"I poured in the whole bottle of drain cleaner and it's still slow. So I'm buying two more."

The real lesson: Most bathroom sink clogs are hair, and a cheap plastic barbed drain strip pulls it out in two minutes. Never mix drain products, since some combinations give off dangerous fumes. Never plunge a drain that has chemical cleaner in it, because the splashback can burn your skin and eyes. If you've already poured something in, tell the plumber before he starts.

"The toilet runs all night. I jiggle the handle. At this point we have a relationship."

The real lesson: Put a few drops of food coloring in the tank and don't flush for twenty minutes. If color shows up in the bowl, it's the flapper, which is one of the cheapest fixes in the house. If not, check that the chain has a little slack and that the water level sits below the top of the overflow tube. (This one's on the list of repairs you should stop paying someone else to do. It's also why I'm here.)

"I bought the pipe wrench because it looked the most serious."

The real lesson: A pipe wrench's teeth will chew up chrome in one turn. Use an adjustable wrench with a rag wrapped around the finish. For faucet nuts tucked up behind the bowl, buy a basin wrench. It looks ridiculous, and it's the only tool that reaches. If your kit doesn't have one yet, the ten tools that cover most household repairs is a good place to start.

"Do you sell a cap for that pipe on the side of the water heater? It keeps dripping."

The real lesson: No joke here. That's the temperature and pressure relief valve, and it's what keeps the tank from failing violently. Never cap it, plug it or remove it. A dripping relief valve means something's wrong with pressure, temperature or the valve itself. Call a licensed plumber.

"My wife said to call a plumber. I said I'd watched a video. Anyway, where do you keep the big buckets?"

The real lesson: She was right, and the counter guy agreed with her before I finished the sentence. Gas lines, main sewer backups, anything behind a finished wall and anything involving the water heater's gas connection belong to a professional. If you ever smell gas, get everyone out, don't flip any switches and call the gas company or 911 from outside. Knowing when to stop is a skill too, and it's cheaper than a ruined ceiling.

Before you go

• The old part, in a bag. Wet is fine. It's the plumbing aisle and nobody will judge you. Matching it on the shelf beats describing it with your hands.
• Two photos from two angles. One of the part where it connects, one wide shot of the whole setup under the sink or behind the toilet. The guy in the apron can read a photo faster than he can read "it's kind of round."
• Measurements written down. Pipe diameter, supply line length, and for a toilet, the rough-in: the distance from the finished wall to the center of the floor bolts. Twelve inches is common, but ten and fourteen exist, and you'll find out the hard way.
• What your pipes are made of. Copper, PEX, CPVC, galvanized steel. Scratch it with a key if you're not sure. Fittings are material-specific, and that's the first question you'll get asked.
• The shutoff, already shut. Turn the water off before you leave the house, not after you come home with the part and an audience.

I did finally ask. The flapper I needed was right in front of me the whole time, one shelf down. The man in the orange apron didn't say a word. He didn't have to.