The smell hit me before I saw the problem—like old fish wrapped in a damp towel. I’d just lifted the chrome trap from Mrs. Patel’s pedestal sink when I noticed the putty: grey, cracked, and weeping like it had given up on life. She’d tried to “refresh” the seal herself with a £2.99 own-brand tub from the corner shop. Two weeks later the cupboard base was swollen like a soaked loaf. That grey smear was the plumbing equivalent of a plaster on a broken leg, and it was my job to rip it off and start again.
I’ve been a City & Guilds Level 3 plumber for eleven years, clocked 1,800 basin swaps, and lost count of how many DIY putty jobs I’ve redone. The worst was a Victorian rental in Clapham where the landlord had used window putty because “it’s all the same stuff, innit?” The tenants kept a roasting tin under the trap to catch the nightly trickle. I carry photos of that disaster on my phone; it convinces sceptical customers that a £6 tube of proper silicone or a £4 pot of fresh plumber’s putty is cheaper than a £450 cabinet replacement.
Quick Steps:
1. Shut off water and place a bucket under the trap.
2. Unscrew the trap or pop-up tailpiece with pump pliers.
3. Scrape off every trace of old putty—plastic scraper, no metal.
4. Roll a 15 mm rope of new putty, press evenly around the flange.
5. Reassemble, tighten hand-plus-quarter-turn, wipe squeeze-out within 5 min.
What Plumber’s Putty Actually Does (and Where It Goes Wrong)
Plumber’s putty is a clay-like sealant that stays permanently pliable. It’s meant to fill microscopic gaps between a fixture’s polished surface and the metal flange of a waste fitting. It is NOT glue; compression does the work. The classic error is using too much and expecting it to harden. I once watched a rookie spread it like peanut butter on a 1½-inch bath waste. The excess oozed into the threads, broke off inside the pipe and blocked the trap six weeks later. The call-out fee cost him more than he earned on the whole bathroom.
The putty also needs to be oil-based; modern “stain-free” versions use limestone and linseed alternatives so they won’t mark granite or composite sinks. If you’re working with porous stone, spend the extra 80 p and buy Oatey “Sta Put” or Everbilt white label—both are £4.20 at Screwfix (2025 price). Cheap grey putty leaches oil and leaves a moon-shaped shadow that no amount of Cif will shift.
Tools and Consumables You’ll Need on One Tray
Forget the kitchen drawer rummage. Lay everything out on a baking tray; the rim stops tiny screws rolling into the abyss.
- 6-inch plastic putty knife – £1.50, Toolstation
- 8-inch adjustable pliers – I use Bahco 9031, £22 but any will do
- 300 mm spirit level – to check if the sink lip is proud (warped MDF tops cause chronic leaks)
- Fresh pot of putty – 14 oz Oatey 31166 is £5.40 on Amazon Prime
- Lint-free rag and IPA spray – removes silicone residue that stops putty grabbing
- Bucket or washing-up bowl – the deeper the better; catches the “grey shower” when you pop the trap
I keep a spare 40 mm McAlpine washer set (WS40, £1.80) in the van. If the old rubber is perished, you’re already halfway through a full swap, so you might as well refresh everything while the water’s off.
Removing the Old Putty Without Scoring Chrome
Chrome plating is only 0.0005 inch thick—less than a cigarette paper. Attack it with a flat-blade screwdriver and you’ll leave tiger scratches that rust within weeks. Instead, grip a plastic scraper like you’re buttering toast and push away from your body. Warm the flange first with a hairdryer on medium; the heat softens ancient putty and halves the labour. For stubborn crumbs, wind 12-gauge copper wire around your finger and use the loop like a shoelace to saw inside the thread groove. The wire is softer than brass, so it won’t gouge.
On pop-up wastes, the pivot rod cup hides a rice-grain bead of putty most people miss. If you leave it, the new seal sits on a bump and weeps. I learned that the hard way on a hotel job in 2019—three callbacks before I spotted the speck.
Rolling and Applying the New Bead: The Sausage Test
Tear off a strip the length of a Bic pen and roll it between your palms until it’s the diameter of a 5 p coin. Too thin and it won’t compress; too fat and it’ll squirt into the bowl like Play-Doh. Lay the rope on the flange, overlap the ends by 5 mm, then twist so the joint disappears. Press lightly—just enough to tack it in place. If you need more than one rope, stagger the joints 120° apart, like tyre valves on a car rim, so no single spot is weak.
Set the waste into the sink hole dead square. Give it a half-twist only, then stop. Over-spinning shears the putty and leaves bare metal. I tighten the back-nut hand-plus-quarter-turn with pliers, never a full rotation. You’ll feel the compression; the putty should ooze slightly. Wipe the squeeze-out within five minutes—after that it skins and smears.
When to Use Silicone Instead (and Why I Sometimes Do)
Some manufacturers—Kohler, Villeroy & Boch—now specify silicone because their sinks have micro-textured rims that putty can’t wet. If the instructions say “use sealant,” obey. I use Dow Corning 785+ (£7.80, 310 ml, white) and run a 3 mm bead. The trick is to let it skin for ten minutes before tightening; otherwise it pumps out like toothpaste and the joint starves.
Silicone is also mandatory on plastic (ABS or poly) wastes. Putty’s oils creep into the polymer and cause stress cracking within a year. I keep a colour-matched tube of Everbuild Everflex for grey fittings; it’s £4.99 at Toolstation and sets in 20 minutes, so the customer can run water the same evening.
Reassembling the Trap: Hand-Tight Plus a Nip
Cross-threading a trap nut is the fastest way to turn a five-minute job into a tap-dance with a hacksaw. Start the nut backwards until you feel the thread click, then spin it on. Once finger-tight, give it an eighth-turn with pliers—no more. Modern traps have a tapered rubber seal; overtightening deforms it and creates a spiral leak path. If the nut still spins after the eighth-turn, the thread is stripped and you need a new trap (McAlpine T5M, £6.40). Don’t PTFE tape the threads; the seal is at the washer, not the flank.
Fill the sink, pull the plug and watch for drips. I wait through two full bowls; the warmth expands the putty and any micro-gap shows up. A single bead of water at the nut means the washer isn’t seating—back off, realign, retighten.
Common Leak Points After You’ve “Fixed” It
The flange looks perfect, yet Sunday morning the customer rings: “It’s dripping again.” Nine times out of ten, the back-nut has relaxed. New putty continues to flow microscopically for 48 hours; check the nut next day and nip it an extra sixteenth-turn. Second culprit is the pivot-rod seal. When you lever the pop-up rod back in, the rubber O-ring can roll. Smear a dab of silicone grease on it first—Swarfega 4309, £2.20 for 100 ml tube lasts me six months.
Finally, check the overflow slot. If the waste is the type with side ports, block the main outlet with a wet rag and fill just the overflow. I’ve seen putty bridges leave a hairline gap that only leaks when the kids slosh water over the rim.
Safety Considerations and Legal Requirements
There’s no Part P for putty, but if you’re working in a rental you must comply with the Landlord and Tenant Act 1985—fit for human habitation includes watertight waste systems. Fail and the tenant can sue for damages. In commercial kitchens, the Water Supply (Water Fittings) Regulations 1999 require you to prevent contamination; that means no putty in contact with potable pipework upstream of the trap.
Warning: Over-tightening a chrome back-nut can fracture the flange → sharp edge slices your palm weeks later → wear cut-level-3 gloves and tighten only an eighth-turn past hand-tight.
Cost and Time: What You Should Pay in 2025
A fresh pot of Oatey putty costs £5.40 and seals three average sinks. My labour rate is £65 first hour, £35 per half-hour after. Ninety per cent of putty reseals take 18–25 minutes, so you’re looking at £65 total if I’m already on site. If you DIY, budget an hour the first time—mostly spent scraping. I charge £120 to fix a botched job where excess putty has blocked the trap arm; the difference pays for a professional but saves you a Saturday and a flooded cupboard.
Can I reuse the old putty if it looks okay?
Never. Once compressed, putty loses its oils and forms micro-cracks. It’s like trying to re-inflate a burst balloon.
Is plumber’s putty the same as window putty?
No. Window putty contains linseed and hardens; it will crack under vibration and leak. Only use products labelled “plumber’s putty.”
How long before I can use the sink?
Immediately. Putty seals by compression, not curing. Run water straight away; it helps seat the seal.
Can I put silicone over old putty?
Bad idea. Silicone won’t bond to oily residue. Strip every trace with IPA first or the joint will slide apart.
My granite sink instructions say “no putty.” What now?
Use a thin bead of low-modulus silicone such as Dow 785+. Wipe the rim with acetone, apply 2 mm bead, assemble wet, tighten, then wipe squeeze-out.
Why does my new seal still smell?
Residual oil from cheap putty can stink for a week. Place a sliced lemon in the bowl overnight; citric acid neutralises the odour.
A pea-sized gap is all it takes to turn a £5 tube of putty into a £500 insurance claim. Roll it right, compress it once, and you’ll forget it’s even there—that’s the whole point. Next time you open the cupboard and the base is bone-dry, give yourself a pat on the back. If it’s not, you know where to find me.
Tony Garcia