How to Reseal a Kitchen Sink (and When to Call a Pro)

The sealant round a kitchen sink takes a beating: hot water, washing-up liquid, scrubbing and the odd splash of bleach, every day. No wonder it’s often the first bead in the kitchen to go yellow, black or split.

The good news is that resealing a kitchen sink is a manageable job if you’re handy and patient. Here’s how we’d do it, what to use, and when it’s worth getting a mastic man in instead.

Signs your kitchen sink sealant needs replacing

You don’t need to wait for a leak. It’s time to reseal if you see any of these:

Black or grey spots in the silicone that won’t scrub off. That’s mould growing in or under the bead, and bleach rarely shifts it for good.
Gaps, splits or lifting edges, especially at the front corners where you lean on the worktop.
A dark line or swelling in the worktop near the sink. On laminate worktops this often means water has already got into the chipboard core.
Water in the cupboard under the sink, when the pipes and taps are dry.

If the worktop has already swollen or gone soft, new sealant won’t fix it. Catching the joint early is what stops it getting that far.

What you’ll need

A sharp blade or sealant removal tool, and a plastic scraper
Silicone remover (optional, but it helps with stubborn residue)
Methylated spirit or a solvent cleaner, and clean lint-free cloths
Masking tape, if you want crisp, straight edges
A good-quality kitchen and bathroom (sanitary) silicone with mould protection, in white, clear or a colour to suit the worktop
A sealant gun and a smoothing tool

Skip decorator’s caulk and general-purpose acrylic. They’re fine for painted skirting, but they aren’t made for a joint that sits in water every day. (If you’ve seen American guides talk about “caulking” a sink, that’s just their word for sealing it.)

How to reseal a kitchen sink: step by step

1. Get all the old silicone out. This is the step most DIY jobs skimp on, and it’s the one that matters most. Cut along both edges of the old bead, peel it out, then scrape off every last bit of residue. New silicone won’t stick properly to old silicone, and any mould left behind will come straight back through.

2. Clean and degrease. Kitchens are greasy places. Wipe the joint with methylated spirit or a solvent cleaner to lift grease, soap and any remover residue.

3. Let it dry completely. Don’t rush this. If the joint is damp the silicone may look fine for a week, then peel away. Ideally leave it overnight and keep the tap off.

4. Mask up (optional). Tape the worktop and sink rim, leaving a neat gap for the bead.

5. Apply one steady bead. Cut the nozzle to suit the gap and push the sealant into the joint in one smooth run per side. Aim for a bead that fills the gap and touches both surfaces, not a fat blob sitting on top.

6. Tool it straight away. Smooth the bead with a tool so it’s pressed into the joint and slightly concave, so water runs off rather than sitting on it. Pull the tape off while the silicone is still wet.

7. Leave it alone. Keep water off it for at least 24 hours, or longer if the cartridge says so. Our post on how long silicone takes to dry explains why.

Kitchen sink sealant: which type?

Black sealant joint between a granite worktop and its upstand, beside a white basin

For most stainless steel and composite sinks in a laminate or wooden worktop, a sanitary-grade silicone with mould protection does the job. We use and apply products from brands such as Arbo and Sika.

Natural stone is different. Some silicones, particularly the vinegar-smelling acetoxy type, can stain or mark granite and marble, so on stone we use a sealant made for it. With quartz and other engineered stone, check what the worktop maker recommends before you start.

On wooden worktops, make sure the timber is oiled and bone dry around the sink cut-out first. Kitchen worktop silicone grips a sealed, dry surface far better.

When to call a professional instead

Bright modern open-plan kitchen and dining room

Resealing a sink is a fair DIY job, but some situations are better left to someone who seals kitchens every week:

Stone or quartz worktops, where the wrong product or a slip with a blade costs a lot more than a reseal.
Undermount sinks, where the joint is under the worktop edge and hard to reach. If the bowl has started to drop, it needs re-fixing before anyone seals it.
Mould behind the sealant, or a worktop that’s already starting to swell.
Wide or uneven gaps, which need the right bead size and sometimes a backing material.
The whole kitchen at once: sink, worktop to wall, upstands and splashback, done in one visit so it all matches.

Our kitchen sealant service covers sinks, worktops and upstands, and we also do worktop and splashback sealant in utility rooms and boot rooms. Every job starts with all the old sealant out and the joints cleaned and dried.

We’re based in Bedford and cover Bedford and the surrounding towns, as well as London, the South East, the Midlands and East Anglia. If you’re searching for a mastic man in Bedford or a mastic man near me, we’re a sealant company with over 20 years in construction behind us and £5m public liability insurance.

Kitchen sink resealing FAQ

How often should a kitchen sink be resealed?
There’s no fixed timetable. Reseal it when you see mould that won’t clean off, gaps, lifting edges or water getting under the rim.

Can I put new silicone over the old?
No. It won’t bond properly and it traps any mould underneath. Always remove the old bead completely first.

How long before I can use the sink?
Leave it at least 24 hours, or whatever the cartridge says if that’s longer.

Why does my sink silicone keep going black?
Usually because old sealant or mould was left behind, the joint was damp when it was sealed, or the product had no mould protection. Doing those three things right makes a real difference.

Get your kitchen resealed properly

Rather have it done once and done right? Call 01234 607 252 or WhatsApp 07757 772 880 with a couple of photos of your sink and worktop, or send us a message through our contact page. We’re open Monday to Friday 8:00 to 18:30 and Saturday 9:00 to 16:00.

Need a hand? Pioneer Sealants can do this for you. See our kitchen sealant, bathroom resealing, window and door mastic pages, or contact our team.