Why This Job Is Easier Than It Looks
Replacing a kitchen faucet is one of the most satisfying weekend projects in the house. It takes basic tools, no plumbing experience, and about 90 minutes if nothing fights you. The reason people pay a plumber $250 for this is not that the work is hard — it is that they have never been under a sink before and do not own a basin wrench.
That is the trick of this whole job: the basin wrench. Without one, you will crawl under the sink, reach up behind the faucet, and discover you cannot turn the mounting nuts because there is no room for any normal wrench. With one, you can loosen them in 60 seconds. Spend the $15 before you start.
This guide walks through the full job from shutting off the water to checking for leaks, including the two pitfalls that wreck most faucet jobs: stripped supply line flare fittings and mounting nuts that are rusted solid.
Tools You Need
You do not need much, but every one of these matters.
The Essentials
- Basin wrench — non-negotiable. This is a long T-handle with a pivoting jaw at the end. It is the only tool that reaches up behind the sink deck to grab the mounting nuts holding the old faucet.
- Adjustable wrench — two of them if you have them. One to hold, one to turn.
- Channellock pliers — for anything the wrenches cannot grip.
- Bucket or shallow tray — catches the water still sitting in the supply lines when you disconnect them.
- Old towels — for the water that misses the bucket, because some always does.
- Flashlight or headlamp — under a sink is dark.
- Penetrating oil — PB Blaster or Kroil. For frozen nuts.
- Razor blade or utility knife — to cut away old silicone or putty under the faucet base.
- Plumber’s tape (PTFE) — wrap the threads on any new connections.
- Silicone caulk or plumber’s putty — whatever the new faucet instructions specify, usually silicone on stainless sinks.
Nice to Have
- Knee pad or folded towel for the cabinet floor. Your back will thank you.
- A phone with the flashlight mounted so both hands are free.
- Safety glasses — old gunk likes to fall in your eyes.
Step 1: Shut Off the Water
Under the sink you will see two supply lines — one cold, one hot — each running to a shutoff valve before going up to the faucet. Turn both valves clockwise until they stop. Most are quarter-turn ball valves now and close in one move; older ones are multi-turn and may need several rotations.
Now open the faucet in both positions (hot and cold) to bleed pressure from the lines. When the water drops from a stream to a trickle to nothing, you are shut off.
If the shutoff valves do not hold — water keeps trickling — you either have a failing valve or you did not fully close it. If closing harder does not fix it, you will need to shut off the house main and plan to replace the shutoff valves at the same time. This is common on houses older than 20 years and is the only thing that can turn a 90-minute job into a 3-hour job.
Step 2: Disconnect the Supply Lines
Put your bucket under the supply line connections. Each supply line has a compression nut where it meets the shutoff valve at the bottom and another where it meets the faucet tailpiece at the top.
Start at the shutoff valve. Use one wrench to hold the valve body still and a second wrench to loosen the compression nut counterclockwise. You must hold the valve, because if the valve rotates on the copper pipe it can break the joint behind the wall and now you have a real problem.
Once the nut is loose, water will drip out. Let it drain into the bucket. Then unthread it by hand the rest of the way.
Move to the top connection at the faucet tailpiece. Same deal — one wrench holds, one turns. Loosen counterclockwise.
If you see braided stainless supply lines, good — they are usually easy. If you see cheap plastic or old chrome lines, expect trouble. Replace them with new braided stainless lines regardless. They are $8 a pair and prevent 90% of future leaks.
Step 3: Remove the Old Mounting Nuts
This is where the basin wrench earns its keep. Lie on your back in the cabinet with your head up near the drain and look up. You will see the underside of the sink deck and two or three large plastic or brass nuts holding the faucet down from below.
Slide the basin wrench up with the jaw open. Let it grab the flat of the nut. Twist the T-handle counterclockwise. The jaw is self-tightening, so it grips harder the more you turn.
Most nuts come loose with moderate force. Once they are free, spin them off by hand and let the faucet lift up from above.
If the Nuts Are Frozen
Old faucets often have mounting nuts that have been damp for 20 years and seized solid. If the basin wrench cannot break them free, do this:
- Spray PB Blaster on the threads. Let it sit 15 minutes.
- Try again. Apply steady pressure, do not jerk.
- Still stuck? Heat the nut gently with a hair dryer or heat gun on low for 30 seconds. Heat expands the nut faster than the threaded shank and breaks the corrosion bond.
- Still stuck? Last resort: cut the nut with a reciprocating saw and a metal blade, or an oscillating multi-tool. Be careful not to cut the sink or the faucet tailpiece if you plan to reuse anything.
I have yet to find a nut that does not eventually give up. Take your time.
Step 4: Lift Out the Old Faucet and Clean the Sink Deck
With the nuts off, the old faucet lifts straight up and out. It will probably be stuck to the sink by 20 years of old silicone or hardened plumber’s putty. Wiggle it free.
Now clean the deck. Scrape off all the old gunk with a razor blade held at a shallow angle. Finish with a rag and some denatured alcohol or rubbing alcohol. The new faucet needs a clean, dry surface so the gasket or seal sits flat. Any lump of old putty under the new base means a wobble or a leak.
Take a good look at the mounting holes now. Check the spacing (usually 4 inches, 8 inches, or a single hole) and confirm it matches what the new faucet is designed for. If it does not, you need a deck plate — many new faucets come with one for this exact reason.
Step 5: Install the New Faucet
Read the instructions that came with your faucet. Seriously. Every brand does the mounting slightly differently. That said, here is the general flow.
- If your faucet comes with a rubber or silicone gasket for the base, set it on the deck. If it calls for silicone caulk instead, run a thin bead around the base footprint on the underside of the faucet.
- Drop the supply lines (already attached to most new faucets) through the mounting hole from above.
- From below, slide the mounting plate or washer up over the tailpiece and thread the mounting nut up by hand first. Hand tight only.
- From above, center the faucet and make sure it is square to the sink.
- Back below, tighten the mounting nut with the basin wrench. Snug, not gorilla-tight. Overtightening can crack a plastic nut or crush the gasket.
If your faucet has a pull-down sprayer, there is usually a weight that clamps to the sprayer hose. Do not forget it — without the weight, the sprayer will not retract back into the faucet head.
Step 6: Connect the Supply Lines
Use new braided stainless supply lines. Match hot to hot (usually left) and cold to cold (right). The line has a nut on each end that is already gasketed — do not use plumber’s tape on these, it can actually prevent a good seal.
- Thread the top end onto the faucet tailpiece by hand until it stops. Then snug it with a wrench — about a quarter turn past finger-tight is usually right.
- Thread the bottom end onto the shutoff valve the same way.
- Do not cross-thread. If it does not start smoothly by hand, back off and realign.
The Stripped Supply Line Problem
Here is the most common disaster: people overtighten the supply line nut with a wrench and strip the threads on the faucet tailpiece or the shutoff valve. Now it will never seal properly.
Avoid this by starting every connection by hand, and stopping the wrench the moment you feel real resistance. Finger tight plus a quarter turn. If it leaks after that, you can always tighten a sixteenth of a turn more.
Step 7: Turn the Water Back On and Check for Leaks
Before you open the shutoffs, remove the aerator from the tip of the faucet (it unscrews, sometimes counterclockwise, sometimes clockwise depending on design — check your instructions). This prevents debris from the supply lines clogging the aerator on first use.
Now open the shutoff valves slowly. Half turn. Listen for hissing. Watch the connections for drips.
Open the faucet on full cold. Water should start in 2-3 seconds with some sputtering as air clears. Let it run for 30 seconds. Switch to hot and run it another 30 seconds. Switch to warm.
Now get under the sink with a flashlight and a dry paper towel. Touch each connection — the faucet tailpiece, the top of the supply line, the shutoff valve, the bottom of the supply line. The towel should come back dry. Watch for a full two minutes because slow leaks take time to show.
If you see a drop, snug that connection a sixteenth of a turn and check again. Do not go crazy with the wrench. Most leaks fix with a tiny tweak.
Once everything is dry, put the aerator back on.
Common Pitfalls and How to Avoid Them
Buying the wrong faucet for your sink. Count your mounting holes before you buy. Three holes with 4-inch spacing is a centerset. Three holes at 8-inch spacing is a widespread. One hole is a single-hole mount. Do not guess.
Forgetting the sprayer weight. As mentioned above — if your new faucet has a pull-down spray, the weight makes it retract. Attach it.
Skipping the basin wrench. You cannot do this job without one. Channellocks and adjustable wrenches cannot reach up behind the sink.
Overtightening everything. Plastic mounting nuts crack. Supply line threads strip. Gaskets crush. Snug, not tight.
Not turning the shutoff valves carefully. Old multi-turn valves can seize or break if you force them. If one snaps, shut off the house main and replace the valve.
Not running water for a full minute before trusting the job. Some leaks only appear after pressure is up and seals have flexed a bit.
Final Thoughts
The whole job is 90 minutes if the nuts come off clean, two hours if they fight you, and half a Saturday if you have to replace shutoff valves too. Compared to a $250 plumber call, this is one of the best hourly returns in home DIY.
Buy the basin wrench once and keep it in your plumbing kit forever. Use new braided stainless supply lines every single time. And check for leaks after the job, then again the next morning before you declare it done.
Water is patient. Give it any chance to leak and it will find one.
