Why the 45-minute faucet job takes an afternoon

Quick answer: For a first-timer, multiply the time on the box by three, count every hardware store trip and every tool you have to buy, then subtract it all from the plumber's labor quote. If what's left divided by your real hours beats what your Saturday is worth, grab the wrench. If not, make the call before you start, not at 7 p.m. with the water off.

The question

The kitchen faucet drips. It's dripped since spring. You can replace it yourself, or you can pay a plumber to do it while you stand nearby and offer to hold the flashlight.

Every number below is an example. Swap in your own quote, your own prices and your own hourly value.

The Dad Math

This is the version done standing at the sink, holding the new faucet box like a winning lottery ticket.

• Plumber's labor to swap the faucet: $250 (example)
• New faucet: $150 (example), and you'd pay that either way, so it doesn't count
• Time printed on the box: 45 minutes
• Money saved: $250
• Effective hourly rate: $250 ÷ 0.75 hours = $333 an hour

At $333 an hour, I'm basically a heart surgeon who works under sinks. I announced this to my wife. She asked, very kindly, whether the 45 minutes on the box was measured on me.

It wasn't.

The real math

Start the clock when the job actually starts, which is when you open the cabinet under the sink and remember that everything you own that's toxic, sticky or half-empty lives there.

Time, honestly logged (example afternoon):

• Empty the cabinet, find the dog's missing tennis ball, wipe up whatever leaked in 2019: 20 minutes
• Close the shutoff valves under the sink. The hot one won't turn. It hasn't moved since the house was built. Find the main shutoff, which you've never touched either: 25 minutes
• Discover the old faucet's mounting nuts are up behind the basin where no human hand fits. Drive to the hardware store for a basin wrench: 45 minutes, round trip plus aisle wandering
• Get the old faucet out: 40 minutes, most of it lying on your back with a flashlight in your teeth
• New faucet needs supply lines, and the old ones are the wrong length and the wrong thread. Second trip: 40 minutes
• Install, tighten, open the valves slowly, watch for drips: 45 minutes
• Find a drip. Snug a fitting a quarter turn. Watch again: 15 minutes
• Put the cabinet back together: 15 minutes

Total: 4 hours, 5 minutes. Call it 4 hours. The box was off by a factor of about five. This is normal. Boxes are written by people who have done it four hundred times, in a lab, with all their parts.

Now put a price on it. Pick an example value for your time. I'll use $30 an hour. You might use your take-home pay, or what you'd pay someone to do a chore you hate.

• Your time: 4 hours × $30 = $120
• Basin wrench: $25 (example)
• Supply lines the plumber would have brought: $15 (example)
• Driving: 2 trips × 10 miles round trip = 20 miles. Say it costs 50 cents a mile to run your truck, all in (example): 20 × $0.50 = $10

DIY cost, not counting the faucet: $120 + $25 + $15 + $10 = $170

Real savings: $250 − $170 = $80

Real hourly rate: $80 ÷ 4 hours = $20 an hour

Still positive. Not surgeon money. More like a teenager's summer job, with worse posture.

The second time is different. You own the wrench now. You know which supply lines to buy, and you bought them before you started. Say it takes 1.5 hours and one trip you don't need:

• Time: 1.5 × $30 = $45
• Parts the plumber would have brought: $15
• Savings: $250 − $60 = $190, or about $127 an hour

This is the part nobody tells you. DIY plumbing gets dramatically cheaper the second time, because the first time you were mostly paying tuition.

The line you can't put a number on. A slow drip from a fitting you didn't quite tighten, running into the cabinet floor for three weeks. I won't invent a figure for it because the figure is "whatever your subfloor and cabinets cost." So build in the habit instead: after any plumbing job, put a dry paper towel under every connection and check it that night and the next morning. A damp towel costs nothing. A soft floor costs a lot.

And the scenario that ruins the whole spreadsheet. You get halfway, the old nut is fused on, the water's off to the house, it's Sunday evening, and you call a plumber. Now you pay the after-hours rate, which at most outfits runs well above the daytime rate (ask what theirs is), plus everything you already bought, plus the four hours you already spent. That's not savings. That's a donation.

The verdict

Use this before you pick up a tool:

Savings = plumber's labor quote − (parts they'd supply) − (tools you have to buy) − (trips × your round-trip cost)

Hours = box time × 3 for a first-timer

If savings ÷ hours is more than your hourly value, do it yourself. If it's close, consider whether you'll do this job again. A tool you'll use five times is a good buy. A tool you'll use once is a rental with extra steps. The BRO cost-per-use calculator will do the division for you if the faucet has already cost you your patience.

Three rules that change the math in your favor:

• Test the shutoff valves the day before. If they won't turn, you just learned the real job, and it might be a valve replacement first. That's a different decision.
• Start Saturday morning. The hardware store is open, and if you have to call for help, you're paying daytime rates.
• Buy the parts before you start. Take a photo of the old connections, read the new faucet's install sheet for the fittings it needs, and have the store match them. That's one trip instead of three.

Faucets, toilet flappers, fill valves, drain traps and garbage disposals are fair game for most handy people. If you're building your kit, these ten tools cover most household repairs, and these five jobs are where DIY pays best.

Some jobs don't go in the calculator at all. Anything involving a gas line, including a gas water heater, is a licensed professional's job. So is anything that needs a torch near framing, work on the main sewer line, or a water heater's temperature-and-pressure relief valve. In many places, water heater replacement also requires a permit, so check with your local building department. When a job sits on that line, this is how to get a quote you can trust.

One more thing. While you're under there anyway, put a strip of tape on each shutoff valve marked HOT and COLD, and write the location of the main on the inside of the cabinet door. Leave the sink better than you found it.

My wife has never needed the note. She found the main shutoff in about nine seconds the day I couldn't. But the next person under that sink might be me.