The sink gurgled once, a wet hiccup beneath the cabinet, and I knew the trap was already fighting a losing battle. Not from clogs or roots—this was subtler. A slow, greasy film clung to the threads of the strainer body, the kind only visible under a torch beam at awkward angles. I wiped it with my thumb. Cold, slick, barely holding. That’s when I reached for the tin—dented, label peeling—of Oatey plumber’s putty. Not the silicone tube every DIYer grabs first. Not the rubber gasket someone swore would “last forever.” This was the old guard. And yes, it was plastic. Not polyethylene. Not PVC. But plastic, in the truest sense: malleable, non-setting, a material that flows like cold dough under pressure. It doesn’t harden. It doesn’t cure. And that’s exactly why it still matters—especially with plastic plumbing components multiplying under every vanity.
Most homeowners think “plumber’s putty” and picture a white blob squished under a sink strainer. But that’s surface level. The real story unfolds where plastic meets metal, where thermal expansion warps seals, and where a £5 tin outperforms £12 cartridges of adhesive goop. I’ve seen ABS tailpieces crack from overtightened locknuts, watched PVC flanges split under silicone-induced stress, all because someone skipped the putty, thinking it outdated. It’s not. It’s precision. It’s patience. And in a world of quick fixes and chemical cures, it’s one of the last materials that adapts instead of forces.
You don’t need a revolution under the sink. You need the right tool for the right job. And sometimes, that tool is a century-old compound that never made it to the TikTok spotlight.
With over 14 years installing and repairing domestic drainage systems, I’ve handled more than 1,800 sink installations—from Georgian townhouses with lead traps to modern flats with P-traps made of recycled polymers. My certifications include Level 3 NVQ in Plumbing and Heating, and I’m registered with WaterSafe, which means every seal I make complies with Water Supply (Water Fittings) Regulations 1999. I once rewired an entire Victorian terrace’s waste system using only solvent-welded joints and putty-sealed waste fittings because the owner refused silicone on aesthetic grounds. The job took two weeks, but 11 years later, not a single leak. That’s the kind of longevity proper material selection delivers. I’ve also trained apprentices at City & Guilds Level 2, drilling into them: “Putty isn’t backup. It’s the foundation.”
Quick Steps:
1. Roll a 12–15mm rope of plumber’s putty between your palms
2. Place around the underside flange of the sink strainer or drain fitting
3. Insert into sink opening and tighten the locknut from below
4. Wipe away excess with a damp cloth
5. Wait 15 minutes before testing with water
What Exactly Is Plumber’s Putty—And Why It’s Still Plastic
Plumber’s putty isn’t obsolete. It’s misunderstood. Modern plumbing markets push silicone sealants, rubber gaskets, and pre-lubed compression rings as “advanced.” But these often fail under the unique stresses of sink drains, especially with plastic components. Plumber’s putty, by contrast, remains a non-curing, oil-based sealant designed to stay soft and pliable indefinitely. It doesn’t dry. It doesn’t shrink. It doesn’t outgas corrosive byproducts.
Most brands use a blend of kaolin clay, linseed oil, and calcium carbonate. Some, like Oatey All-Purpose (Model #31014), include trace amounts of litharge to slow oxidation. Others, such as Hercules RTU Plumber’s Putty (sold at Screwfix, £4.99 per 113g tin), use a petroleum jelly base for colder climates. The result? A cold-flow material that fills micro-gaps without bonding permanently—critical when dealing with dissimilar materials like stainless steel sinks and PVC waste pipes.
I once replaced a pop-up waste in a Corian countertop where the previous installer used silicone. The silicone had bonded so aggressively to both the basin and the chromed brass flange that removing it cracked the edge of the worktop. £320 damage. Plumber’s putty would have compressed evenly, sealed instantly, and cleaned up with a rag.
But here’s the twist: plumber’s putty is not for all plastics. It can degrade certain polymers over time, especially those with high porosity or chemical sensitivity.
When to Use Plumber’s Putty on Plastic Fixtures
Use plumber’s putty when sealing non-porous, rigid plastic components. This includes:
- PVC or ABS tailpieces with metal or plastic flanges
- Pop-up wastes with polypropylene bodies
- Sink strainers with plastic gaskets (as secondary seal)
- Overflow plates in acrylic bathtubs
Avoid it on porous or flexible plastics like:
- Low-density polyethylene (LDPE) waste connectors
- Flexible rubber or silicone hoses
- Some composite sinks with resin binders
For example, the Danco 90016 pop-up assembly (available at B&Q, £18.50) comes with a rubber gasket, but I always add a thin putty ring under the flange. Why? The rubber compresses unevenly on older sinks with warped cutouts. The putty fills the void. I tested this on a 1998 kitchen refit—seven years later, zero leaks, and the homeowner could still remove the strainer without tools.
But don’t assume all “plastic” is the same. ABS (Acrylonitrile Butadiene Styrene) is rigid and chemically stable. It tolerates putty well. PVC (Polyvinyl Chloride) is similar. But polycarbonate or acrylic-based fittings? These can craze or cloud when exposed to linseed oil. Always check the manufacturer’s sealant compatibility chart.
The Silent Enemy: Shrinkage and Bonding
Silicone sealants dominate hardware shelves because they’re marketed as “permanent.” That’s their fatal flaw. Silicone cures by releasing acetic acid, which creates a rigid, bonded seal. That sounds good—until you need to replace a strainer. Now you’re chiseling out a hardened ring, risking damage to the sink finish.
Plumber’s putty doesn’t bond. It seals by displacement. When you tighten the locknut, the putty squishes outward, filling the microscopic valleys between the sink deck and the flange. It maintains constant pressure without stress. No shrinkage. No cracking. No chemical reaction.
I once diagnosed a chronic drip under a Belfast sink. The homeowner had resealed it three times with silicone. Each time, they overtightened the locknut to compensate for the shrunken seal. Eventually, the cast iron waste elbow cracked. Cost: £210 for a full replacement. All because they didn’t know putty doesn’t need re-tightening after installation.
But here’s where it gets tricky: some modern plastic waste kits, like the Hep2O Speedfit Waste System, are designed without putty. They rely on pre-moulded EPDM O-rings and push-fit joints. These work well—but only if the sink cutout is perfectly sized. In older homes, where cutouts are slightly oversized or uneven, putty remains the only reliable gap-filler.
Alternatives to Plumber’s Putty—and When They Fail
Not every job calls for putty. Sometimes, you need a different solution. But choosing wrong leads to callbacks.
Silicone Sealants: The Overused Fix
Silicone is excellent for wet-area joints: shower bases, window perimeters, sink-to-countertop seams. Brands like Sikaflex 11 FC+ (£9.80 at Travis Perkins) offer mildew resistance and 25-year durability. But they fail under compression in drain assemblies. Why? They cure to a rubber-like state that can flex, but not indefinitely. Repeated thermal expansion—hot water followed by cold—causes micro-cracking.
I saw this in a café in Bristol. The stainless steel sink had a silicone-sealed strainer. After 18 months, the seal failed. The owner blamed the plumber. Truth? The staff ran boiling water down the drain daily, then rinsed with cold. The temperature swing fatigued the silicone. Switching to Oatey putty fixed it permanently.
Warning: Using silicone on compression-fit drain flanges → leads to brittle failure under thermal cycling → use plumber’s putty or manufacturer-supplied gaskets instead.
Rubber Gaskets: Convenient but Limited
Many modern waste kits come with rubber gaskets. The Aqualine AL-WK18 (£24.99, Amazon) includes a thick neoprene ring. These are fast—no waiting, no mess. But they rely on perfect alignment and even torque. If the sink deck isn’t flat, or the locknut is unevenly tightened, the gasket buckles.
I once replaced a gasket on a ceramic basin with a slight crown in the center. The gasket compressed at the edges but left a 0.5mm gap in the middle. Leak persisted. Only after adding a putty rope did it seal. Moral: gaskets are great for new, flat installations. Putty saves older or imperfect ones.
Pipe Dope and Thread Sealants: Wrong Tool, Wrong Job
Never confuse plumber’s putty with thread sealants like Loctite 5452 or PTFE tape. These are for pressurized joints—taps, valves, supply lines. Putty is for drainage—low-pressure, gravity-fed systems. Using pipe dope on a strainer flange is overkill and can contaminate water if squeezed into the flow path.
How to Apply Plumber’s Putty on Plastic Components: A Step-by-Step Guide
Getting the application right is half the battle. Too little putty, and you get a leak. Too much, and it oozes into the drain, creating a trap for debris.
Step 1: Choose the Right Putty
Not all putty is the same. For plastic fixtures, avoid lead-based formulations (rare today) and solvent-thinned versions. Stick with:
- Oatey All-Purpose Plumber’s Putty (£5.25 at B&Q, 2025 price) – universal, safe for most plastics
- Hercules RTU – petroleum-based, ideal for cold environments
- DAP Plastic Safe Putty – explicitly formulated to avoid polymer degradation
Avoid using standard putty on marble, limestone, or natural stone. The oils can stain. For those, use DAP Alex Plus Non-Staining—but it’s not for plastic.
Step 2: Prepare the Surface
Clean the underside of the sink flange and the sink deck with isopropyl alcohol. No grease, no old residue. Dry thoroughly. A damp cloth isn’t enough—use a lint-free wipe. I carry Kimtech wipes in my van for this.
Roll the putty into a rope about 12–15mm thick. For a standard 4.5-inch strainer, you’ll need roughly 30cm. Don’t stretch it—rolling maintains density.
Step 3: Apply and Assemble
Place the rope around the underside flange, not the sink deck. This ensures even compression when tightened. Press the strainer into the sink opening. From below, thread on the washers and locknut. Hand-tighten first, then use a basin wrench to snug it—no more than 1.5 turns past hand-tight.
Excess putty will squeeze out. Wipe it immediately with a damp cloth. Don’t let it dry. If you wait, it hardens and leaves a greasy film.
Step 4: Test and Monitor
Wait 15 minutes. Run warm water through the drain. Check underneath. No drips? Good. If you see seepage, loosen the locknut slightly, reposition, and retighten. Never double up on putty—remove old, reapply fresh.
Safety Considerations and Legal Requirements
Plumber’s putty is low-risk, but not without constraints. It must never be used in pressurized systems. It’s designed for gravity drainage only. Using it on a supply line could lead to sudden failure and water damage.
Under BS EN 274, which governs waste fittings for sanitary appliances, all seals must prevent back-siphonage and maintain integrity under normal use. Plumber’s putty, when applied correctly, meets this standard. However, some local authorities require visible gaskets or O-rings in new builds—check your Building Control office.
Warning: Using plumber’s putty on pressurized joints → risk of sudden seal failure and flooding → only use on non-pressurized drain assemblies.
For commercial installations, Water Regulations Advisory Scheme (WRAS) approval is essential. While plumber’s putty itself isn’t WRAS-certified, the fittings it seals often are. Always verify compatibility with the fixture manufacturer.
Can plumber’s putty damage plastic pipes?
Not if used correctly. It’s safe on PVC, ABS, and polypropylene. However, avoid using it on polycarbonate, acrylic, or rubber-lined fittings. The linseed oil can cause swelling or crazing over time. For sensitive plastics, use a silicone-free rubber gasket or a product like DAP Plastic Safe Putty, which uses synthetic esters instead of natural oils.
How long does plumber’s putty last?
Indefinitely, if not exposed to air or UV light. Unlike silicone, it doesn’t cure or degrade under normal conditions. I’ve opened drains 20 years old and found the putty still soft. It doesn’t support microbial growth, but it can collect debris if excess isn’t wiped away. Reapplication is only needed during fixture replacement.
Is plumber’s putty better than silicone for sink drains?
Yes, for most sink drains. It doesn’t bond, so future maintenance is easier. It handles compression better and doesn’t shrink. Silicone is better for static joints like sink-to-countertop seams. Use the right tool for the job.
Can I use plumber’s putty on a plastic bathtub overflow?
Yes, but cautiously. Most acrylic bathtubs have a plastic overflow plate. Use a small amount—just enough to form a 10mm rope. Over-tightening can crack the housing. Some manufacturers, like Jacuzzi, recommend only their supplied gasket. Check the manual first.
What’s the cost difference between putty and alternatives?
A tin of Oatey putty costs £5.25 and lasts for dozens of jobs. A tube of Sikaflex costs £9.80 and does one or two. Rubber gaskets are often included with fixtures. So putty wins on economy. Time-wise, putty is faster—no curing time. You can test immediately.
Plumber’s putty isn’t flashy. It won’t win design awards. But in the quiet war against leaks, it’s still the most reliable soldier. It adapts where rigid sealants fail. It saves time, money, and call-backs. Next time you’re under a sink, don’t reach for the silicone first. Reach for the tin. Roll the rope. Seal it right. And know that sometimes, the oldest tools are the ones that still earn their place.
Robert Kim