The silicone seam around a sink is a consumable. It lasts 2–4 years, then darkens, grows mold, cracks and peels off. Through a failing seam, water creeps into the wall, into the cabinet, into the drywall — and a year later you are looking at a swollen vanity or "blooming" wallpaper in the next room. Replacing silicone is cheap prevention that many people skip and then repair the fallout instead.
When to redo the sealant
- The seam has darkened and grown mold. Black specks have bedded deeply into the silicone — cleaning no longer works, only replacement.
- Cracks along the seam. The silicone is "tired", the elasticity is gone, fine tears have appeared.
- Peeling from the wall or sink. If you run your finger along and the silicone "lifts off" in a strip, water is already getting behind it.
- Dampness inside the cabinet walls. Open the vanity and check the inner walls: if the wood is damp or darkened, silicone is leaking.
- Silicone is more than 3–4 years old. Even if everything looks fine, it is better to refresh it pre-emptively before problems surface.
Where a sink is sealed
- Between the sink and countertop/wall — the external seam. The most visible and the one that blackens.
- Between the drain and the sink — a hidden seam under the drain grate. Often leaks in older drains.
- Between the faucet and the sink — under the faucet nut. Leaks rarely, but when it does, water pools in the vanity.
- "Tile-to-countertop" joint at the wall behind the sink — if the tile is vertical, this joint must be silicone, not grout.
How silicone replacement is done
- Removing the old silicone. A utility knife and a plastic scraper cut away the whole mass. Thin residues are softened with a solvent (white spirit, denatured alcohol) and scraped off.
- Degreasing and drying. The surface is wiped with alcohol and dried. Moisture is the main enemy of adhesion.
- Masking with tape. Masking tape is applied on both sides of the future seam — this gives a straight line and protects surfaces from excess silicone.
- Applying silicone. From a gun, in an even bead.
- Shaping the seam. A plastic tool or a soapy finger (liquid soap with water) smooths the bead into a concave profile.
- Removing the tape. Before the silicone cures.
- Curing. Full cure — 24 hours. The sink can be used after 3–4 hours, but leaving it longer is better.
Which silicone to use
- Sanitary (kitchen/bath) with an anti-mold additive — mandatory for bathroom and kitchen. Look for "sanitary", "fungicide", "anti-mold" on the tube.
- Neutral (oxime) — no vinegar smell, does not attack ceramic or chrome. Slightly more expensive but universal.
- Acetic (acidic) — cheaper, strong smell, may leave marks on sensitive materials (marble, bronze). Acceptable for a sink but not the best choice.
- NOT "construction" or "universal" from the hardware aisle — those are not sanitary, mold appears within a month.
Color: usually clear or white. For black sinks, black silicone is available from good manufacturers — Soudal, Ceresit, Tytan.
What it costs in Israel
- Perimeter silicone replacement for one sink — 150–300 ILS
- Sink sealing + "tile-to-countertop" joint — 200–400 ILS
- Drain and faucet sealing (with grate/nut removal) — 250–450 ILS
- "Full package" — all bathroom seams (sink, bathtub, shower) — 500–900 ILS
- Standalone call-out (a 20-minute job) — usually a minimum charge of 200–300 ILS applies
Can you do it yourself
Yes, this is one of the few plumbing jobs you can actually do yourself without serious risk. You will need:
- A caulking gun (35–60 ILS at Ace or Home Center).
- A tube of sanitary silicone (20–40 ILS).
- A utility knife, a plastic scraper, masking tape, wipes, alcohol.
The job takes 30–45 minutes plus 24 hours of cure time. Main DIY mistakes:
- Old silicone was not fully removed — the new one does not grip.
- The surface was not degreased — after two months it peels off.
- Seam too thick — mold breeds in it.
- Using the sink after an hour — water reaches fresh silicone and it never sets.
If not sure, call a technician. A pro does it in 30 minutes and gives a 1–2 year warranty.
How to make silicone last longer
- Wipe the seam dry after shower or dishwashing (when you can) — 100% humidity kills silicone fast.
- Once a week — a vinegar solution or anti-mold spray over the seam. Not straight bleach — it damages silicone.
- Do not put hot pots on the "tile-to-countertop" joint — silicone loses elasticity at 150+ °C.
- Bathroom ventilation — open the door or window after showering so humidity drops back to 60% at least once a day.
FAQ
Can I just "refresh" the silicone by applying a new bead over the old?
No. Fresh silicone does not bond to old silicone — it holds for the first week, then peels off in a strip. The old silicone is always removed completely, that step is mandatory.
Is black mold on the seam a health hazard?
Mold spores get into the bathroom air and can trigger allergies and respiratory issues — especially in children and people with asthma. Replace the silicone before mold "moves in" deep. If it already has, do not try to bleach it — that is temporary, only replacement works.
How often should sealing be renewed?
On average every 2–3 years. In a bathroom without extraction and with constant humidity — every 1.5 years. In a kitchen, where silicone suffers less from humidity but more from grease — every 3–4 years. Judge by the state of the seam, not only by age.
Does the technician warranty the new silicone?
Good technicians — yes, for 1–2 years. That means if the seam cracks or lifts early, they come back and redo it at no charge (assuming normal use). Confirm when booking.