Plumbers don't pay for stuff that's not getting wet, dirty, or both. That's the whole shopping list, basically. An NYC tenement basement in Staten Island or anywhere else in the boroughs is the worst-case stress test — six-foot ceilings, cast iron stack from 1923, a sump that hasn't worked since the Bloomberg administration, and you're going to be on your back inside a closet that smells like a closet from 1923.
Start with the boots, because if your feet are wet you're useless by lunch. We sell a lot of Muck Chore Classic to plumbers and a lot of the Tingley 31151 17-inch rubber for guys who are wading. For the dry-ish jobs, a waterproof leather work boot — Timberland Pro Pit Boss waterproof, or the Carhartt CMF6366 6-inch composite-toe waterproof — those are the ones that come back for re-orders. Steel toe is your call but most plumbers I see buy composite because you're around water all day and a steel toe is a heat sink in winter and a rust factory year-round.
Pants. Carhartt Washed Duck Double-Front B136. Reinforced knees because you're kneeling on a concrete floor with bits of pipe under it. Plenty of guys also like the Dickies 85-283 painter pants for the loose fit and the room for kneepads. Avoid stretchy slim-cut pants — you're going to be straddling a stack and the inseam is going to give out in three weeks.
Shirts: a long-sleeve henley or a worn-in button-up. Plumbers tend to come in for the Carhartt K128 long-sleeve henley because it'll wick a little, won't snag on a pipe wrench, and you can pull the sleeves up. A short-sleeve T leaves your forearms exposed to whatever's dripping out of the joint you just opened, and you do not want that.
Layering for a basement that's 55 degrees and damp: a fleece or a hoodie under a Carhartt detroit jacket. The basement won't get warmer once you're in it, so don't over-layer. You're going to sweat under PVC primer and that's its own problem.
"Plumbers don't pay for stuff that's not getting wet, dirty, or both."
Gloves are a bigger deal for plumbers than people realize. Nitrile-coated work gloves for general use — we like the Showa 377 or the Atlas Fit 300. They grip a wet pipe, they're cheap enough to throw away when you punch through a clog. For propane torch work and soldering, a leather welder's glove or a goatskin Tillman 1338. Don't use the same gloves for both. The nitrile gets near a torch and you've got melted glove on your hand.
Knee pads. Non-negotiable. The Klein Tradesman gel pads or the ToughBuilt GelFit Thigh Support. Plumbers kneel more than tilers and tilers wear pads, so wear them.
Eye and respiratory: ANSI Z87 wraparounds because you're going to be looking up while a chunk of cast iron rust falls in your face. A 3M 7500 half-face respirator with P100 filters if you're cutting cast or breathing in dry sewer line — yes, really, the dust off old cast iron is not great and the fumes off lead joints are worse.
Hat: a low-profile bump cap, not a hard hat, for low-ceiling work. The Ergodyne Skullerz 8945 is what we stock most. A real hard hat keeps catching on joists and you'll take it off, which defeats the purpose.
One last thing: bring two of everything that's a consumable. Two pairs of gloves, two pairs of socks (merino, like the Darn Tough Hiker Boot Sock, because you'll change them at lunch), two shirts. A wet plumber is a slow plumber, and your boss is paying you by the hour but he is not paying you to be slow.