Plumber's Putty vs Silicone - The Critical Difference Nobody Explains
When to use putty, when to use silicone, and why using the wrong one causes leaks. A NYC plumber clears up the confusion.
Pro Tip from 30+ Years
Fun Facts
- Plumber's putty never fully hardens. That's the point - it stays soft and pliable so you can remove fixtures for maintenance without chiseling through cured sealant.
- Silicone caulk was originally developed for industrial sealing applications in the 1940s. Its use in plumbing grew in the 1970s as formulations improved.
- Plumber's putty can stain marble, granite, and porous stone countertops. If you have stone surfaces, use a stain-free putty formulation or silicone instead.
Two Products, Completely Different Jobs
Plumber's putty and silicone caulk both create seals around plumbing fixtures. But they work differently, serve different purposes, and using the wrong one creates problems. Here's the breakdown.
Plumber's Putty
What it is: A soft, clay-like compound that stays pliable indefinitely. It creates a watertight seal between a fixture and the surface it sits on.
Where to use it:
How to use it: Roll putty into a rope about 1/4-inch thick. Wrap the rope around the underside of the drain flange or faucet base. Press the fixture into place - the excess putty squeezes out around the edges. Wipe the excess with a rag.
Key advantage: Stays soft. When you need to replace a drain assembly 5 years later, the putty scrapes off easily. No chiseling, no chemicals, no wrestling with cured silicone.
Cost: $3-$6 per can. Oatey and Hercules are the standard brands.
Silicone Caulk
What it is: A flexible, rubbery sealant that cures permanently. Creates an adhesive, waterproof bond.
Where to use it:
How to use it: Apply with a caulk gun, smooth with a wet finger or tool, let cure for 24 hours before water contact.
Key advantage: Flexible and adhesive. Handles movement between surfaces (tub expanding with hot water, tile shifting slightly) without breaking the seal.
Cost: $5-$12 per tube. Use 100% silicone (not "silicone blend" or "latex caulk with silicone"). GE Supreme and DAP are solid choices.
The Mistake Everyone Makes
Using silicone where putty belongs: If you silicone a sink drain flange instead of using putty, you'll curse yourself when you need to replace that drain. Cured silicone bonds to the sink surface and requires scraping, razor blading, and solvent to remove. Putty wipes off in 30 seconds.
Using putty where silicone belongs: Putty between a tub and wall tile will fail. It can't handle the movement, it doesn't adhere, and water will find its way behind the tile. This is silicone territory.
The Toilet Debate
There's an ongoing debate in plumbing about whether to caulk a toilet base to the floor. NYC code requires it. The argument against: if the wax seal fails, caulk traps water under the toilet where you can't see it, causing hidden damage. The argument for: caulk prevents water from getting under the toilet from cleaning, and it looks cleaner.
My take: caulk the front and sides, leave the back open. If the wax seal leaks, water escapes from the back where you'll notice it before it causes major damage. You get the clean look and the safety valve.