“Stainless steel doesn’t stain,” the supplier laughed when I called about a ring-shaped shadow around a brand-new kitchen sink. I’d just finished a full refurb in a Hackney flat—quartz worktops, undermount Franke Orion 1.5-bowl, brushed-finish taps that cost more than my first van—and the client spotted a dull grey halo the morning after we connected the waste. My heart sank faster than the pop-up plug. Turned out the shadow wasn’t water marks; it was the oils from the cheap generic putty the apprentice dolloped on the basket strainer. Stainless is tough, but it’s also a drama queen: leave petroleum residue sitting on a 1.2 mm brushed deck and the chromium oxide film sulks for days. That phone call taught me to treat plumber’s putty stainless steel applications like a first date: use the right product, keep it brief, and clean up before you leave.
I’ve been a City & Guilds Level 3 plumbing & heating engineer for twelve years, clocking roughly 2,400 installs across London and Essex. I’ve pulled apart Victorian lead traps, chased pin-hole leaks through 28 mm microbore, and resealed more basket wastes than I’ve had hot dinners. That Franke sink episode is one of hundreds where the wrong putty turned a five-minute polish job into an hour-long chemistry lesson. In this article I’ll show you which putties are safe for stainless, where to use them (and where not), how much to apply, and what mistakes void your warranty—so you never have to explain a ghost-grey ring to a client.
Why Standard Putty Can Mark Stainless Steel
Traditional plumber’s putty is basically powdered clay mixed with linseed or soybean oil. The oil keeps the clay pliable, but it also migrates into porous surfaces—think granite, marble, or the microscopic grain lines on a brushed stainless deck. Once the oil creeps in, you’re not polishing a surface film; you’re trying to lift grease out of tiny grooves. Brushed finishes are the worst because the satin grain gives the oil more “tooth” to hang on to.
Manufacturers know this. Blanco’s fitting instructions for the Silgranit sinks actually warn against oil-based putty, and Franke will reject a cosmetic discolouration claim if they find petroleum residue. The safe route is to use a stainless-safe, oil-free putty—usually labelled “non-staining” or “stainless approved”. Oatey’s Sta-Put Ultra, Everflow’s non-stain, and Screwfix’s No. 5 are three I keep in the van. They swap the linseed for a polymer filler that cures slightly, so it stays flexible but doesn’t bleed. Price? About £6–8 for a 400 g tub, double the cost of basic putty, but still cheaper than a replacement £260 sink.
Where You Should and Shouldn’t Use Putty on Stainless
Basket Strainers and Waste Outlets
Undermount or inset, the lip of a basket waste needs a seal between the flange and the sink deck. I run a 5 mm rope of non-stain putty around the underside of the flange, then press and twist so the excess squeezes out evenly. Wipe the overhang immediately with a dry microfiber—never a wet rag, because water thins the oils you’re trying to avoid. On a top-mount sink you can flip the bowl over and do the same; gravity helps the putty fill micro-gaps.
Tap Holes and Deck Plates
Some plumbers swear by silicone for taps, but I like putty on stainless because it’s reversible. If a client upgrades to a three-hole tap later, you can pop the deck plate off without slicing through a bead of silicone. Roll a pencil-thin snake, circle the base of the escutcheon, then tighten the tap nuts. The trick is to snug, not over-tighten—excessive torque squeezes all the putty out and leaves a metal-to-metal ring that can sweat.
Never on Press-Fit or Compression Joints
Putty is a gasket, not a glue. Don’t use it on 15 mm compression olives or press-fit connectors. If the joint relies on a rubber O-ring (like most modern bottle traps), putty will actually prevent the ring from seating and you’ll get weeping. I once had to redo a full trap set because the previous installer packed the threads with putty, thinking “more sealant equals more seal”. The client paid twice—my labour plus the call-out to the first cowboy.
Step-by-Step: Sealing a Stainless Sink Waste with Non-Stain Putty
1. Dry-fit everything—basket waste, washers, cardboard friction ring—so you know the threads engage fully.
2. Roll a 5 mm rope of Oatey Sta-Put Ultra, long enough to circle the flange twice. Overlap the ends, then pinch so the join disappears.
3. Insert the waste tail through the sink hole, press down and twist 180° each way. You should see a thin, even collar of putty.
4. From below, slide on the rubber washer, then the cardboard friction ring, then the back-nut. Hand-tighten until you feel resistance, plus an extra quarter-turn with pump-pliers and a washcloth (protects the chrome).
5. Wipe the squeeze-out with a dry paper towel, then buff the stainless with WD-40 Specialist Stainless Polish to lift any micro-residue.
6. Run a full bowl of hot water, release it, and inspect from below. Any weeping means the nut needs another eighth-turn—not more putty.
Tip: If you’re working in cold weather, warm the putty tub in your pocket first. Cold polymer putty skins and won’t flow into scratches.
Common Mistakes That Void Warranties
Using generic putty and blaming the sink. Manufacturers test with approved sealants; they can spot oil bleed under magnification. Keep the tub label and photo the finished joint—your insurance if a claim arises.
Over-tightening. Stainless is thin; too much torque warps the flange and creates a rocking waste. Franke specifies 8 Nm—about the force you’d use on a spark plug. If you don’t own a torque wrench, snug plus a firm quarter-turn is close enough on a 1½-inch nut.
Leaving the excess. Putty hardens slightly but never fully cures. A bead left around the flange collects crumbs, looks amateur, and eventually discolours. I finish with a plastic razor so no metal touches the brushed surface.
Cost Comparison: Putty vs. Silicone vs. Rubber Gaskets
A 400 g tub of non-stain putty (£7) seals roughly 15 basket wastes—about 45 p per job. A 300 ml tube of Dow 785+ silicone is £9 and does 8–10 wastes, but you need a gun, masking tape, and curing time. Rubber sealing gaskets (Franke part 114.0290.473) cost £4 each and are reusable, yet they sometimes spin when you tighten, pinching the rubber. My preference: putty for reversible jobs, silicone for permanent stone installs, gasket only if the manufacturer supplies one pre-fitted.
Alternatives When Putty Isn’t Suitable
Silicone works if the sink edge is perfectly flat and you can clamp the waste overnight. I use GE Momentive Semi-Fluid 100 on granite because it skins in 20 min and won’t slump. PTFE tape is useless here—compression threads seal on the olive, not the thread peaks. And never use hemp and paste; the linseed in the paste stains worse than putty.
Safety Considerations and Legal Requirements
In the UK, sink waste seals aren’t governed by Water Regulations directly, but WRAS approval is required for any material in contact with potable water. Non-stain putties from Oatey and Everflow carry WRAS certification; generic pound-shop putty often doesn’t. If you’re working on a commercial kitchen, you’ll need a compliance certificate for insurance.
Warning: Oil-stained stainless can mislead a client into thinking the sink is rusting. They reach for abrasive cream cleaners, scratch the grain, and then you really have a corrosion issue. Always test putty on an off-cut first.
Can I use normal plumber’s putty on a stainless sink?
Only if you enjoy polishing grey halos. Standard linseed-based putty stains brushed finishes within hours. Spend the extra ÂŁ3 on non-stain and keep your warranty intact.
How long does non-stain putty last?
Once compressed, it stays flexible for 20+ years. I’ve removed 15-year-old Sta-Put that still felt like fresh Blu-tack. Heat accelerates curing, so don’t use it next to a cooker hob cut-out.
Is putty better than silicone for waste flanges?
Putty is reversible and faster—no cure time, no masking. Silicone gives a thinner, invisible joint but needs 24 h before you run water. For rental flats or same-day handovers, putty wins.
Will non-stain putty work on composite sinks?
Yes, but composite is less porous so the risk of staining is lower. I still use it for consistency; one tub covers every job in the van.
Can I paint over plumber’s putty?
No. Putty never fully hardens, so paint skins and cracks. If you need a painted seal, use acrylic caulk instead.
How do I remove old putty from stainless?
Plastic razor blade first, then a dab of WD-40 on a microfiber to dissolve oil residue. Finish with Fairy Liquid and warm water—never wire wool.
Stainless steel looks bullet-proof until the wrong blob of putty ghosts your £300 sink. Keep a tub of WRAS-approved, non-staining putty in the van, apply a modest rope, and clean the squeeze-out before the client sees it. Do that and the only thing reflecting in the brushed finish will be your smiling face, not a greasy halo. Grab a tub next time you’re in branch, test it on an off-cut, and you’ll sleep easier knowing your install won’t star in someone’s one-star review.
Tony Garcia