What do you use to seal a faucet to a sink?

Quick Answer

To properly seal a faucet to a sink, you need to use plumber’s putty or silicone caulk. Plumber’s putty is the most common option and creates a watertight seal that prevents leaks. Silicone caulk can also work, but may not adhere as well on certain surfaces. Proper application of the putty or caulk is key – you need to fully seal around the faucet hole before installing the faucet.

What is Plumber’s Putty?

Plumber’s putty is a moldable, clay-like sealant that is designed specifically for creating watertight seals in plumbing applications. It is made from chalk and linseed oil and has a doughy, clay-like texture when applied. Here are some key features of plumber’s putty:

• Creates watertight seal – The main purpose of plumber’s putty is to prevent leaks. When pressed into place, it forms a tight seal that water cannot penetrate.
• Moldable – Plumber’s putty can be rolled and pressed into any shape or size needed to fit plumbing fixtures and fill gaps.
• Stays pliable – The putty remains pliable and workable after application. This allows you to ensure a tight seal around complex shapes.
• Easy to apply – Plumber’s putty can be applied by hand without any special tools. Just roll it into a “rope” and press it into place.
• Long lasting – Once dried, plumber’s putty maintains its seal for many years. It does not crack or break down over time.
• Non-toxic – Plumber’s putty is safe for potable water use and contains no toxic chemicals.

Because of these useful properties, plumber’s putty is found in almost every plumber’s toolkit. It is the go-to product for sealing most plumbing fixtures, including faucets, strainers, and stoppers. When applied properly, it prevents leaks over years of use.

How to Apply Plumber’s Putty Under a Faucet

Here are the steps for correctly applying plumber’s putty to seal a faucet:

1. Clean sink surface – Use a razor blade or putty knife to scrape away any old putty or caulk remnants from the faucet hole area. The area should be clean and dry for the putty to adhere.
2. Apply putty – Roll some plumber’s putty into a rope about 1/2 inch in diameter. Press the rope onto the underside rim of the faucet baseplate so it sticks and fully surrounds the hole. Use your fingers to smooth the putty and create a uniform seal.
3. Install faucet – With the putty in place, lower the faucet into the hole and press down firmly. The putty will flatten and mold around the faucet base. Secure the faucet in place with the retaining nut or screws.
4. Tighten & clean up – Fully tighten the retaining nut or screws to compress the putty evenly underneath the faucet. Scrape away any excess putty squeezed out during installation with a putty knife.
5. Allow putty to dry – Let the plumber’s putty cure and dry for 24 hours before using the faucet. The putty will harden to create a watertight seal.

The key is to create a ring of plumber’s putty that fully seals the underside of the faucet to the countertop surface. Take care to smooth out the putty and compress it firmly when installing the faucet. Wipe away any excess. Once dried, the putty will prevent water from seeping underneath the faucet.

Tips for Applying Plumber’s Putty

Here are some useful tips to get the best results when sealing a faucet with plumber’s putty:

• Apply enough putty – Be sure to apply a sufficient amount to seal the entire faucet hole circumference. Skimping on putty could lead to leaks.
• Press putty into shape – Before installing the faucet, press the putty firmly into the rim to flatten and smooth it. Eliminate any gaps or thin spots.
• Avoid trapping air bubbles – Air bubbles in the putty can allow leaks. Press out any bubbles and voids when smoothing the putty.
• Use putty for stainless steel sinks – Plumber’s putty works better than silicone for stainless steel sinks. Silicone may not adhere well to stainless steel.
• Consider silicone for cultured marble – Silicone caulk may work better than plumber’s putty for cultured marble and composite sinks.
• Watch for granite – Use a plastic washer between plumber’s putty and granite sinks. The oils in the putty can stain granite.
• Give putty time to cure – Allow at least 24 hours for complete curing and hardening of the putty before running water.

Taking the time to properly apply plumber’s putty and following these tips will result in a reliable, leak-free seal for the faucet install.

Using Silicone Caulk Instead

In some cases, clear silicone caulk can also be used to seal a faucet. Here are some pros and cons of using silicone caulk instead of plumber’s putty:

Pros

• Good adhesion – Silicone caulk adheres well to many surfaces including porcelain, fiberglass, acrylic, and even stainless steel.
• Waterproof seal – When cured, silicone provides a watertight seal to prevent leaks.
• Neat appearance – Clear silicone is less visible than the white plumber’s putty once dried.
• Fills gaps – The caulk can easily fill wider or uneven gaps.

Cons

• Hard to apply – Smoothing silicone neatly under a faucet can be challenging due to its sticky texture.
• Peeling hazard – Silicone may peel away from certain surfaces over time, compromising the seal.
• Slow drying – Complete curing takes up to 48 hours so faucet can’t be used right away.
• Weak seal – Seal may break over time and lead to leaks.

In general, plumber’s putty remains the top choice for sealing faucets. But in some cases, such as cultured marble sinks, silicone caulk is also an acceptable option if applied carefully. Regardless of the material used, following the proper application technique is vital for creating a reliable seal.

Signs of Plumbing Leaks Under the Faucet

Even with proper sealing, leaks can sometimes occur under a faucet over time. Here are some signs that may indicate leaking from an improperly sealed faucet:

• Visible water damage – Swelling, bubbling or discoloration of the countertop material around the faucet.
• Pooling water – Water collecting underneath on the cabinet or backsplash when the faucet is used.
• Dripping water – Visible drips or moisture under the faucet and on sink edges.
• Rust accumulation – Rust build up around faucet holes or mounting hardware.
• Mold or mildew – fungal growth in the areas surrounding the faucet.
• Sink movement – Sink feels less stable and rocking or movement occurs when in use.

If any evidence of moisture damage or leaking is noticed near the water supply valves or drain connections, the plumbing beneath the sink should also be inspected. Catching leaks early is important to prevent water damage and mold growth.

Fixing a Leaky Faucet Seal

If you discover leaking coming from under the faucet, the seal will need to be repaired:

1. Turn off water supply – Turn off the hot and cold shutoff valves underneath or behind the sink before making any repairs.
2. Remove faucet – Unscrew the retaining nut or faucet screws and carefully lift the faucet off the sink.
3. Clean & dry area – Use a razor blade to fully scrape away all the old putty or caulk from the underside of the faucet and sink surface.
4. Apply new sealant – Apply fresh plumber’s putty or silicone and make sure it fully seals the faucet hole before reinstalling the faucet.
5. Check for issues – Examine the faucet hole for any cracks or defects that could affect sealing. Use silicone underneath on porous material.
6. Install & seal faucet – Press the faucet back into place, securing it firmly hand tightening nuts/screws. Do not overtighten.
7. Wait for cure time – Allow the new sealant to fully cure before using the faucet. Check for leaks.

Taking proper care when resealing the faucet and following the procedure correctly will prevent further leakage issues. Avoid overtightening faucet hardware during reassembly which can crack sinks.

Preventing Leaks When Installing a New Faucet

When installing a brand new faucet, proper sealing techniques are key for preventing leaks over its lifetime:

• Carefully read manufacturer instructions for the faucet and sink materials.
• Check sink surface for flatness – Grind down any high spots around faucet holes.
• Use putty for stainless steel sinks or silicone for cultured marble vanities.
• Completely seal the underside before setting the faucet.
• Align faucet properly before tightening down hardware.
• Do not overtighten nuts or screws to avoid cracking sink.
• Remove any excess putty or caulk for a clean look.
• Let sealant fully cure for 24-48 hours before use.
• Start with cold water first when testing out new faucet.

Taking extra care during the installation process will get the faucet sealed correctly on the first try and ensure leak-free operation for years before resealing is needed.

Conclusion

Properly sealing a faucet to a sink is crucial to preventing leakage issues and water damage over time. In most cases, plumber’s putty is the best product to use to create a watertight seal between the faucet and countertop. Just be sure to fully seal around the faucet hole before installation. Silicone caulk can also work in some applications. Careful sealing during faucet installations and prompt repair of any leaks can add years of drip-free performance to a sink. With the right materials and procedures, you can certainly avoid the nuisance of a leaky faucet.