Shut off the hot and cold stop valves under the sink, open the faucet to drain pressure, then disconnect the supply lines and sprayer. Remove the mounting nuts from below with a basin wrench, lift out the old faucet, set the new one with its gasket, reconnect, and leak-check.
What tools and parts you need first
Lay everything out before you crawl under the sink. Trips back to the garage waste time and leave water dripping where you do not want it.
- Basin wrench: the key tool. Its long shaft and pivoting jaw reach the mounting nuts high up behind the sink bowl, where a normal wrench cannot fit.
- Adjustable wrench or channel-lock pliers for the supply-line nuts.
- Bucket and towels to catch the water left in the lines and the trap area.
- Flashlight or headlamp so you can see the connections.
- Plumber's putty or silicone, plus the new faucet's gasket or base plate.
- PTFE thread tape (also called plumber's tape), used only where it belongs (more on that below).
- A new faucet that matches your sink's hole count. A three-hole sink needs either a three-hole faucet or a single-hole faucet with a deck plate that covers the extra holes.
Buy the faucet to fit the deck, not the other way around. Counting the holes in your sink or countertop before you shop saves a second trip and a return.
How to shut off the water and drain the lines
Turning off the water is the first real step, and it is the one people skip at their own cost. Look under the sink for two small stop valves, also called angle stops, one on the hot line and one on the cold. Turn each one clockwise until it stops. Then open the faucet on top and let it run until the flow dies to nothing. That drains the pressure trapped in the lines so the supply connections come apart cleanly.
If the sink has no stop valves, or the valves are seized and will not seal, shut off the main water valve to the house instead, then open the faucet to relieve pressure. For the steps to find and close a fixture or main shutoff, see our guide on how to shut off water to a fixture.
Put your bucket under the connections before you loosen anything. Even drained lines hold a little water, and a towel in the bottom of the cabinet keeps that water off the wood. Old stop valves sometimes weep a few drops after you close them; that is common and not cause for alarm, but it tells you the valve is aging.
How to remove the old faucet
With the water off and the lines drained, disconnect from the bottom up. Loosen the supply-line nuts where the lines meet the faucet shanks, using your adjustable wrench while steadying the line so it does not twist. If a side sprayer or a pull-down hose is attached, disconnect it too, along with any quick-connect clip the maker used.
Now reach up with the basin wrench and loosen the mounting nuts that clamp the faucet to the deck. Older nuts may be crusted with mineral scale; Phoenix tap water is hard, so expect buildup. If a nut will not budge, a shot of penetrating oil and a few minutes of patience usually frees it. Once the nuts are off, lift the old faucet straight up and out.
Scrape the deck clean. Old putty, dried silicone, and a ring of hard-water scale all need to come off so the new faucet seats flat and seals. A plastic putty knife and a rag with a little white vinegar cut through the calcium. Kohler notes that mineral and lime deposits are a routine problem on faucets in hard-water areas, so a clean, scale-free deck gives the new gasket a fair chance to seal. Wipe the surface dry before the new faucet goes down.
How to set and connect the new faucet
Feed the new faucet's lines and shanks down through the deck holes, seating its gasket or base plate against the sink so the trim sits square. Most modern faucets use a rubber gasket and need no putty, but check the instructions; some still call for a thin bead of plumber's putty or silicone under a metal base plate.
From below, thread the mounting nuts on by hand, then snug them with the basin wrench. Hand-tight plus a firm quarter turn is usually enough. Delta's kitchen faucet instructions are blunt about overdoing it: "Do not overtighten." Forcing the nuts can crack a plastic shank or warp the base, so stop when the faucet sits firm and does not rock.
Reconnect the supply lines to the correct shanks, hot to hot and cold to cold. Here is where thread tape matters. Use PTFE tape only on tapered pipe threads (the older threaded connections that seal metal-on-metal). Do not wrap tape on the rubber-gasket flex lines that most faucets ship with today; those braided supply lines seal with a rubber washer or a cone fitting, and tape only gets in the way. Hand-thread each connection first to avoid cross-threading, then snug it with a wrench. Reattach the sprayer or pull-down hose and clip the weight on per the diagram.
How to test for leaks and when to call a plumber
Turn the water back on slowly. Reopen the under-sink stop valves a little at a time rather than all at once, then run the faucet through hot, cold, and the sprayer. While the water runs and again after you shut it off, feel every connection with a dry finger or a paper towel: the supply nuts, the faucet base, and the stop valves themselves. The first wet spot is your leak. A connection that weeps usually needs another light turn of the wrench, not brute force.
A like-for-like swap, replacing a faucet without moving or changing the pipes behind the wall, usually needs no permit, because you are not altering the plumbing system. Rules vary by city, so confirm with your local building department if you are unsure.
Stop and call a licensed plumber when the job stops being a simple swap. The two common triggers are corroded stop valves that will not shut off, which means the water cannot be isolated safely, and any situation where the supply piping itself has to be modified to fit the new faucet. A pro can replace failed angle stops or rework the lines without risking a leak inside the cabinet. HQ Plumbing & Air (Arizona ROC #355170) serves metro Phoenix and offers 24/7 service if a shutoff fails on you mid-project. If the new faucet's handle feels stiff after the swap, that is a separate issue; see our page on what to do when a faucet handle is hard to turn.
One last note on flow. New faucets sold today meet federal and EPA WaterSense efficiency rules, and per EPA a bathroom faucet carrying the WaterSense label uses no more than 1.5 gallons per minute versus the older 2.2 gpm standard. Kitchen faucets run a touch higher for filling pots, but the same efficiency push means your new faucet will likely use less water than the one you pulled out.