What You Need Before You Start

Replacing a Delta bathroom faucet is a task most homeowners can do in an afternoon with basic tools. You will need an adjustable wrench, a Phillips head screwdriver, a flathead screwdriver, and a bucket or towel to catch water. Some Delta models also need a hex wrench (Allen key), which usually comes in the box with your new faucet. Turn off the water supply under the sink before you begin — look for two shut-off valves, one for hot and one for cold, and turn both clockwise until they stop.

Before you buy a replacement faucet, measure the distance between the holes on your sink or countertop. Most bathroom faucets are either 4 inches (center-to-center on the outer holes) or 8 inches apart. If you have a single hole, you need a single-hole faucet. Check whether your current faucet is mounted on the sink itself or on the countertop — this affects which Delta model will fit. Take a photo of your existing setup to show the hardware store or to reference while shopping.

Key Takeaways

  • Turn off both hot and cold water shut-off valves under the sink before disconnecting anything.
  • Remove the old faucet by unscrewing the supply lines with an adjustable wrench and unbolting the faucet body from underneath the sink.
  • Clean the sink or countertop thoroughly before installing the new faucet to prevent leaks around the base.
  • Hand-tighten all connections first, then use your wrench to snug them — over-tightening causes cracks and leaks.
  • Test both hot and cold water and check for drips under the sink before you consider the job finished.

Removing the Old Faucet

Once the water is off, turn on the faucet handle to release any remaining pressure in the lines. Place your bucket or towel under the sink to catch water that will spill when you disconnect the supply lines. Look under the sink for the flexible hoses (usually braided metal or rubber) that connect the shut-off valves to the faucet. Use your adjustable wrench to loosen the nut where each hose connects to the faucet — turn counterclockwise. You may need to hold the fitting on the faucet side steady with a second wrench so it does not spin.

Next, locate the bolts or nuts that hold the faucet body to the sink or countertop. On most Delta faucets, these are underneath the sink and accessible from below. You may see a large nut or a series of smaller bolts. Use your wrench or hex wrench to remove them. If the faucet has a decorative collar or escutcheon (the ring around the base), you may need to unscrew or pry it off first. Once all bolts are removed, the old faucet should lift out from the top. If it is stuck, gently rock it side to side rather than forcing it.

Cleaning and Preparing the Sink

With the old faucet out, you will see the mounting holes and possibly old caulk or mineral deposits around the base. Use a flathead screwdriver or putty knife to scrape away any old caulk, plumber's putty, or debris. Wipe the area clean with a damp cloth and let it dry completely. This step is important — leftover material under the new faucet base will create gaps where water can seep underneath and cause damage to your cabinet or countertop.

If your new Delta faucet comes with a rubber gasket or foam ring, place it on the faucet body now, before you insert the faucet into the hole. This gasket creates a watertight seal. Some Delta models use plumber's putty instead — if yours does, roll a thin rope of putty and press it around the underside of the faucet collar before installation. Check your faucet's instruction sheet to see which method applies to your model.

Installing the New Delta Faucet

Insert the new faucet through the mounting hole or holes from the top of the sink. If you have a widespread faucet (three separate pieces), install the spout first, then the hot and cold handles. Align the faucet so the spout points straight ahead and the handles are level. From underneath the sink, hand-tighten all mounting bolts first — do not use your wrench yet. This lets you adjust the faucet position if needed before you lock it down.

Once the faucet is centered and level, use your wrench to tighten the mounting bolts. Tighten in a crisscross pattern (like tightening a car wheel) so the faucet sits evenly. Snug each bolt firmly, but do not over-tighten — you are looking for a find fit, not maximum force. Over-tightening can crack the faucet body or strip the threads. If you hear a cracking sound, stop when ready and loosen the bolt slightly.

Connecting the Water Supply Lines

Now reconnect the hot and cold water supply lines. If your new faucet came with new hoses, use those instead of the old ones — they are sized correctly for the new faucet connections. Hand-tighten the nut where each hose connects to the faucet inlet. Once hand-tight, use your adjustable wrench to turn the nut an additional quarter turn. Again, snug is better than tight. If you over-tighten and crack the fitting, you will have a leak that requires replacing the hose.

Double-check that both hoses are connected — hot water to the hot inlet, cold to the cold inlet. The inlets are usually labeled on the faucet body or in the instruction sheet. If you reverse them, your hot and cold handles will be backwards. Once both hoses are connected, turn the shut-off valves counterclockwise to restore water pressure. Open the faucet handle slowly and let water run for 10 to 15 seconds to flush out any debris from the lines.

Testing for Leaks

Turn both the hot and cold handles through their full range of motion and check that water flows smoothly and temperature changes as expected. Look under the sink with a flashlight and watch for drips at the supply line connections, at the faucet base, and at any other joints. A small drip that stops after a few seconds is normal — the lines are settling. A steady drip means a connection is loose and needs another quarter turn with your wrench.

If water is leaking from under the faucet collar (where it meets the sink), the gasket or putty did not seal properly. You will need to remove the faucet, clean the area again, and reinstall with a fresh gasket or putty. This is frustrating but not difficult — it is the same process you just completed. Leave the faucet running for a minute, then check again. If everything is dry after five minutes, your installation is complete.

Common Mistakes to Avoid

The most common error is forgetting to turn off the water before disconnecting the supply lines — this floods your cabinet and makes the job much messier. The second is over-tightening bolts and connections, which cracks fittings and creates leaks that are harder to fix than the original installation. A third mistake is reversing the hot and cold supply lines, which is straightforward to do and annoying to discover after you have finished.

Another frequent problem is installing the faucet without cleaning away old caulk or putty. Water seeps under the base, rots the wood underneath, and the faucet becomes loose within weeks. Finally, some people skip the test step and do not discover a leak until water damage appears in the cabinet below. Spend five minutes checking for drips — it saves hours of repair work later.

Frequently Asked Questions

Do I need to turn off the water at the main if I cannot find the shut-off valves under the sink?

Yes. If the shut-off valves are missing or broken, turn off the main water supply to your house. The main shut-off is usually in the basement, crawlspace, or outside near the water meter. Once you have replaced the faucet, ask a plumber to install shut-off valves under the sink — they cost about $50 to $100 and make future repairs much easier.

What if water leaks from the base of the faucet after I install it?

Remove the faucet, scrape away all old caulk and putty from the sink, and dry the area completely. Reinstall with a fresh gasket or new plumber's putty. If leaking continues, the sink or countertop surface may be uneven — a shim (thin wedge) under the faucet collar can help seal the gap.

Can I reuse the old supply lines with a new faucet?

You can, but new hoses are inexpensive and come with your faucet. Old hoses may have mineral buildup inside or weak connections that fail under pressure. Using new hoses reduces the risk of leaks.

How tight should I make the connections?

Hand-tighten first, then use your wrench to turn each nut about a quarter turn more. If you can turn it with your fingers after that, it is not tight enough. If you need to strain with the wrench, it is too tight. The goal is snug, not maximum force.

What if the new faucet does not fit the holes in my sink?

You may have measured wrong or chosen the wrong faucet type. Measure the hole spacing again and check whether the sink is drilled for a 4-inch, 8-inch, or single-hole faucet. Return the faucet and choose the correct model. If the holes are damaged or in the wrong place, a plumber can drill new ones.