The scent hit me first—earthy, faintly oily, like damp clay left in a tin near a radiator. It wasn’t unpleasant, just unmistakable. I’d opened a decades-old toolbox at a job in Croydon, one abandoned in a basement since the 1980s, and there it sat: a hardened lump of something greyish-brown, crusted around the edges, in a dented aluminium cup. No label. No instructions. Just putty. That moment made me pause. We still use plumber’s putty every day, yet few plumbers—let alone homeowners—ever stop to ask what’s actually in it. Most assume it’s just a greasy blob that seals things. But the ingredients matter. They determine where it works, where it fails, and why some brands cost £8 at Screwfix while others go for £15 at R.S. Pro. I’ve seen taps leak, drains fail, and fixtures crack because someone used the wrong type—or worse, assumed all putty was the same. Let’s pull back the curtain on what’s really in that tin.
I’ve been a qualified plumbing contractor for 14 years, licensed under Water Regulations Advisory Scheme (WRAS) and certified to Level 3 NVQ in Plumbing and Heating. Over that time, I’ve installed over 1,800 sink traps, seals, and waste fittings where plumber’s putty was the primary sealant. One job in East London stands out—a Victorian townhouse renovation where the client insisted on vintage-style ceramic basins. The drain flanges were brass, hand-finished, and £320 each. We used a zinc-oxide-based putty from Oatey instead of the cheaper clay filler, and it’s still leak-free five winters later. That’s the difference understanding ingredients makes. It’s not just tradition; it’s chemistry, compatibility, and long-term performance.
Quick Steps:
1. Identify the material of the fixture (porcelain, stone, plastic).
2. Choose putty based on ingredients: clay and linseed oil for general use, synthetic polymers for stone.
3. Avoid latex or silicone-based putties on porous surfaces.
4. Roll a ½-inch rope and press into the underside of the flange.
5. Install immediately—don’t let it sit exposed.
What’s Actually in Plumber’s Putty?
Plumber’s putty isn’t one single formula. It’s a category of sealants with wildly different compositions depending on brand, price, and intended use. At its core, it’s a non-hardening, pliable compound designed to fill microscopic gaps between a sink strainer, drain flange, or pop-up assembly and the countertop or basin. But the ingredients vary more than most realise.
The most common base is kaolin clay, a fine white clay used in ceramics and even toothpaste. It’s cheap, abundant, and holds shape well. When blended with linseed oil—a natural drying oil derived from flaxseed—it becomes malleable and water-resistant. This combo is found in budget options like B&Q’s own-brand putty (£4.99 for 113g) and Hancock Plumber’s Putty (£5.80 at Toolstation). It works fine on stainless steel and porcelain sinks. But there’s a catch: linseed oil can bleed over time, especially in warm conditions. I once had a callout six months after a kitchen install because a beige stain had spread under a white Corian countertop. The culprit? Linseed oil migrating through a hairline gap. Not a structural failure, but a cosmetic nightmare.
Synthetic Alternatives: The Rise of Polymer-Based Putties
To solve the bleeding issue, manufacturers developed synthetic putties using polybutene or petroleum jelly as the base instead of linseed oil. These don’t oxidise or leach. Oatey Top Secret (£12.99 for 140g at Plumb Center) uses a proprietary blend of synthetic rubber and mineral oil. It stays put, doesn’t stain, and is safe for use on granite and marble—unlike traditional putty, which can discolour natural stone due to oil content.
Then there’s Gasoila SB-14, a red synthetic putty used in industrial settings. It’s non-toxic, NSF 61-certified, and contains no vegetable oils. Plumbers in commercial kitchens swear by it for grease traps and stainless steel basins where hygiene is critical. It costs £18.50 per tin (225g) from R.S. Pro, but lasts longer because you use less. I used it during a café refit in Brighton—no stains, no shrinkage, even after constant hot water exposure.
Additives That Make the Difference
Beyond the base, additives determine performance. Zinc oxide is common in premium putties like Oatey Knock-Out. It acts as a mild bacteriostatic agent and improves cohesion. You’ll feel it in the texture—smoother, less crumbly. Calcium carbonate is added as a filler to control density and reduce cost. Some brands, like Loctite Plumber’s Putty, mix in talc to reduce tackiness, making it easier to handle.
But here’s what most don’t know: some putties contain latex. This is a problem if you’re sealing near rubber gaskets or using it on people with latex allergies. Always check the SDS (Safety Data Sheet) online. I once had a client with a severe allergy—turned out the putty we’d used had latex derivatives. Switched to Gasoila SB-14, which is latex-free, and the issue vanished.
When Ingredients Dictate Application
Not all materials play nice with all putties. This is where ingredient knowledge becomes critical.
Porcelain and Ceramic: Stick to Traditional
For standard bathroom sinks and ceramic basins, traditional clay-and-linseed putty works perfectly. The surface is non-porous, so oil migration isn’t an issue. Hancock or B&Q’s version are fine here. Roll a ½-inch rope, press it into the underside of the strainer, and tighten. Done.
Granite, Marble, and Quartz: Avoid Linseed Oil
Natural stone is porous. Even polished granite can absorb oils over time, leading to dark rings under the seal. That’s why linseed oil-based putties are a no-go. Use Oatey Top Secret or Gasoila SB-14 instead. They’re formulated to stay contained. A job in a Surrey penthouse taught me this the hard way. Client had a £4,000 quartz sink. We used standard putty. Three months later, a faint halo appeared. Replaced it with Oatey Top Secret—no further issues.
Plastic and Composite Sinks: Beware Solvents
Some putties contain solvents that can degrade acrylic or PVC. Check the label for “safe for plastics.” Loctite Clear Silicone Plumber’s Putty is actually a hybrid—it’s silicone-based, not traditional putty, but marketed as such. It’s safe for all surfaces but cures hard, so it’s not reusable. I prefer Gasoila SB-14 for plastic—it stays pliable and doesn’t react.
Brand Comparison: What You’re Paying For
| Brand & Product | Price (2025) | Base Ingredients | Best For | Notes |
|---|---|---|---|---|
| B&Q Plumber’s Putty | £4.99 (113g) | Kaolin clay, linseed oil | Porcelain, stainless steel | Bleeds slightly; not for stone |
| Hancock Plumber’s Putty | £5.80 (113g) | Clay, linseed oil, talc | General use | Smooth texture; widely available |
| Loctite Plumber’s Putty | £7.20 (120g) | Clay, mineral oil, talc | Plastic-safe option | No linseed oil; less bleeding |
| Oatey Top Secret | £12.99 (140g) | Synthetic rubber, mineral oil | Granite, marble, composites | No staining; NSF 61 certified |
| Gasoila SB-14 | £18.50 (225g) | Polybutene, calcium carbonate | Commercial, food-safe | Latex-free; excellent cohesion |
You’re paying for formulation stability, not just volume. Oatey Top Secret costs more, but one tin lasts two jobs on stone sinks. B&Q’s version? I’ve seen it dry out in the tin after six months in a damp van.
Safety Considerations and Legal Requirements
Plumber’s putty isn’t regulated under building codes like electrical or gas work, but material compatibility falls under Water Supply (Water Fittings) Regulations 1999 in the UK. Using a non-compliant sealant that contaminates drinking water can make you liable. Always use WRAS-approved products when near potable water systems.
Warning: Using linseed oil-based putty on natural stone → causes permanent staining → use synthetic, stone-safe putty instead.
While plumber’s putty isn’t pressurised like a pipe joint, improper sealing can lead to water damage, mould, and structural rot—especially under kitchen sinks. If you’re working in rental properties or new builds, your work could be inspected. I’ve had building control officers check sealant types during final inspections. They didn’t ask for receipts, but they did poke the putty with a screwdriver and sniff it. Yes, really.
Can plumber’s putty be used on threaded pipes?
No. Plumber’s putty is for static, non-pressurised seals only—like sink strainers or drain flanges. It will wash out under pressure. For threaded pipes, use PTFE tape or pipe dope like Loctite 55 Thread Sealing Cord. I’ve seen DIYers try to seal a leaking tap spindle with putty. It held for a day. Then flooded the cupboard.
How long does plumber’s putty last?
Indefinitely, if not exposed to air or water. Once installed, it can last 20+ years. But it dries out if left in an open tin. I keep mine wrapped in cling film inside a sealed container. Old putty turns crumbly and won’t seal. Test by rolling a small ball—if it cracks, bin it.
Is there a latex-free plumber’s putty?
Yes. Gasoila SB-14 and Oatey Top Secret are both latex-free. Always check the SDS sheet online. I keep a PDF folder on my phone with SDS for every product I use. Client in Bristol had a latex allergy—glad I could prove the putty was safe.
Can I use silicone instead of plumber’s putty?
Sometimes. Silicone creates a permanent, watertight seal. Great for showers or where vibration is an issue. But it’s not repositionable. If you need to remove the strainer later, you’ll have to cut through the silicone. Putty allows disassembly. For a rental property where tenants might need access, I use putty. For a high-end wet room, I’ll silicone it.
What’s the difference between plumber’s putty and pipe joint compound?
Plumber’s putty is soft, non-hardening, and used for compression seals. Pipe joint compound (like Rydstrom Pipe Joint Compound) is for threaded metal pipes, contains sealants and lubricants, and often hardens. They’re not interchangeable. I once saw a trainee use pipe dope on a pop-up drain. It oozed into the basin every time they ran the tap. Nightmare to clean.
Knowing what’s in your putty isn’t just trivia—it’s job security. The right choice prevents callbacks, protects expensive fixtures, and builds trust. I don’t reach for the cheapest tin anymore. I match the chemistry to the job. Whether it’s a £30 ceramic sink or a £5,000 marble vanity, the seal is only as good as the ingredients holding it together. Next time you twist open that tin, take a second to read the label. Your reputation depends on it.
Tom Jenkins