Why is water getting under the rim of my kitchen sink?

Whether the sink has lifted, the bead has failed or the tap is the source, and how to reseal a sink rim so it lasts.

Difficulty: beginner
Time: 1 hr 30 min
Read: 4 min
Safety: caution

Short answer

Press down on the sink rim. If it moves, the clips have loosened or one has fallen off and the sink is lifting off its bead. If it is solid, the silicone has failed and needs cutting out and replacing properly. If neither, the water is coming down the tap body rather than through the rim.

Water under a sink rim is a small problem for about six months and then a very expensive one, because it is sitting directly on the raw cut edge of the worktop. Finding which of three routes it is taking is quick, and every one of them is fixable in an afternoon.

Safety

Water reaching the cut edge of a laminate worktop damages it permanently and quickly, so this is urgent rather than cosmetic. Isolate the water before disturbing the tap or the waste, and check the cupboard base and the wall behind before assuming the leak is only at the rim — a sink that has lifted has often been leaking underneath for months.

What you'll need

Sealant remover, a scraper and a blade
Neutral-cure silicone and a gun
Screwdriver and a torch
Masking tape (optional)
Kitchen roll, for tracing the leak
Replacement sink clips, if any are missing (optional)

Step by step

Trace the water before touching anything.Dry everything, lay kitchen roll along the underside of the rim inside the cupboard, and around the tap tails and the waste, then use the sink normally for a day. Where the paper wets tells you which of the three routes it is.
Press the sink rim firmly in several places.Any movement at all means the sink is lifting off its silicone bead as it is loaded. Look underneath: a clip has come loose, sheared, or fallen off, or the clips were never tightened evenly.
Count and check the clips.Most inset sinks use six to ten clips. Check each one is engaged in its channel and tight. Replacements are generic and cost very little, and a sink with three clips doing the work of eight will always leak.
Rule out the tap as the source.Water running down the outside of a tap body, past a perished base washer, appears at the rim and looks identical to a rim leak. Dry the tap base, run the tap, and watch. A wobbly tap almost always means a failed base washer.
Check the waste and the overflow.A weeping waste flange or an overflow hose that has come off wets the underside of the sink and the worktop from below. Look up at the underside of the worktop around the aperture with a torch.
If the seal has failed, cut it all out.Blade round the whole rim, release the clips, lift the sink out, and scrape every trace of old sealant from both the worktop and the sink rim. Then use a silicone remover on the residue — the invisible film is what makes a new bead fail.
Inspect and reseal the cut edge while the sink is out.This is the opportunity. Look at the exposed chipboard edge for softness or swelling, dry it thoroughly, and seal the whole depth with clear silicone or an edge sealer.
Rebed the sink on a continuous bead.One unbroken ring of neutral-cure silicone, sink dropped in, clips tightened progressively around the rim, squeeze-out wiped immediately with a wet finger.
Leave it to cure before using it.The tube will say. Sanitary silicone needs to skin and then cure through, and filling the bowl in the first few hours pulls the fresh bead apart at exactly the point you were sealing.
Check the worktop honestly afterwards.If the cut edge was already soft or the surface around the sink is raised, the worktop has already taken damage and resealing only stops it getting worse. Plan for that rather than being surprised by it.

If it doesn't work

Sink rim moves when pressed

Cause: Clips loose, sheared or missing — Fix: Tighten or replace the clips, working round progressively. If the bead has already been broken by the movement, cut it out and reseal.

Water at the rim only when the tap runs

Cause: Water running down the tap body past a failed base washer — Fix: Replace the base washer under the tap and tighten the tap fixing. A wobbly tap is the usual sign.

Black mould in the sealant line

Cause: Water sitting in a failed joint — Fix: Mould in silicone is through the material, not on it. Cut the whole bead out and replace with a sanitary grade sealant containing a fungicide.

Cupboard base wet but the rim is dry

Cause: Waste, overflow or tap tail connection, not the rim — Fix: Dry everything and trace with kitchen roll under each joint. Waste flange and overflow hose are the usual culprits.

Worktop edge feels soft around the aperture

Cause: The core has already absorbed water — Fix: Reseal to stop it worsening, but the damage is permanent. Plan for a worktop section replacement.

Questions people ask

How do I reseal a kitchen sink?

Cut the old sealant out completely, release the clips and lift the sink, scrape both surfaces clean and use a silicone remover on the residue, seal the exposed cut edge of the worktop, then rebed the sink on one continuous bead of neutral-cure silicone and tighten the clips progressively.

Why does my kitchen sink leak around the edge?

Three possibilities: the clips have loosened so the sink lifts off its bead, the silicone has failed and needs replacing, or water is running down the tap body past a perished base washer. Kitchen roll left under each area for a day identifies which.

Can I just run new silicone over the old?

No. Silicone does not bond to cured silicone, and the new bead lifts within weeks. The old sealant has to be cut out completely and the residue removed chemically before anything new will stick.