How to apply silicone sealant on a bath or basin
Updated: 23 October 2026
You are resealing a bath, a shower or a basin, and the last white bead failed where it met old silicone or a damp rim. How to apply silicone sealant is mostly the hour before you pull the trigger: a bare, dry joint, one continuous bead, and one tooling pass while the paste is still wet. A surface that feels dry is not a cured joint. The [Silicone white comparison](/hub/fillers-adhesives-and-sprays/silicone-white) is the table of cure lines, including the listings that print none. A qualifying purchase through our amazon.co.uk links can earn us a commission at no extra cost to you.
You are resealing a bath, a shower or a basin, and the last white bead failed where it met old silicone or a damp rim.
You are resealing a bath, a shower or a basin, and the last white bead failed where it met old silicone or a damp rim. How to apply silicone sealant is mostly the hour before you pull the trigger: a bare, dry joint, one continuous bead, and one tooling pass while the paste is still wet. A surface that feels dry is not a cured joint. The Silicone white comparison is the table of cure lines, including the listings that print none. A qualifying purchase through our amazon.co.uk links can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Format | Cure on the listing | How you apply it | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Unibond UniBond Triple Protection silicone, white, 291 g | Cartridge, 291 g | Touch dry 20 min, 24 h | Gun, pull tape at once | 9.4 | about £13.49 | View offer |
 Sika Sika sanitary silicone, white | Cartridge | Not stated | Gun, no cap once open | 9.6 | about £7.69 | View offer | |
 151 151 white silicone tube, 70 g | 70 g squeeze tube | 24 h full cure | No gun, cut near 1.5 mm | 9.0 | about £3.35 | View offer |
On this page
Take the old bead off completely
A skim of new silicone over a black bead splits along the old edge. Cut the old sealant back to a clean shoulder, then degrease. White spirit is the wipe, not a substitute for cutting. Work slowly so you do not gouge an acrylic rim, then let the solvent flash off. A damp cloth is not the same step. Soap scum left in the corner is the film the new bead will not stick to. If the bath has dropped, cleaning will not pull it back up to the wall. The fungicide claim is on the bathroom page.
Fill the bath and keep it full
An empty bath sits higher than a full one. If you seal it empty, the first proper fill pulls the rim down and the bead tears. Soudal's note and UK fitter guides say to fill the bath before you seal it, and to leave the water in until the bead has cured. That is trade practice, not a clause in BS EN 15651. A shower tray that rocks when you stand in it splits the same way.
Fill to a normal level and keep that water in for the cure, not just for the hour you are tooling. Masking tape only works if it comes off while the paste is wet. Have the tool on the side before you start. A trip to the cupboard is how a skin forms mid-run.
One bead, then tool it while it is wet
Cut the nozzle to the gap. On the 151 tube, one reviewer went to about 1.5 mm. Pull one continuous bead. Screwfix warns against stopping mid-run. If you stop, overlap into wet paste.
Tool at once, with a finger or a profiler. On a hot day the paste can skin before you pause, and a rushed profiler leaves a ripple. If the skin has formed, cut that section out. Acetoxy smells of vinegar. Ventilate. GOV.UK does not expect harm from correct household use of acetic acid vapour.
Skin time is not shower time
Skin is the surface going dull. Cure is the bead going through. The Soudal six-pack states 7 minutes to initial hardening and 24 hours to a full cure. UniBond states 20 minutes and 24 hours. Dowsil 785 and the £3.35 151 tube state 24 hours. Sika sanitary, Siroflex, the Soudal three-pack, Shopstop and Enócilis state no cure time. Do not lend the 7-minute line to a blank row.
Everbuild 500's sheet talks about 3 mm in 24 hours, and the amazon listing does not print that. When the listing is blank, wait at least 24 hours, and longer if the bead is deep. Do not shower because the surface feels dry.
Stop if the substrate is wrong
Stop if you are about to scrub scratched acrylic, if the surround is natural stone and the cartridge does not say it is safe there, or if water is already under the tray. Dow 785's sheet excludes natural stone. UniBond's sheet claims stone and the amazon listing does not, so follow the document you will rely on. A cartridge will not pull a dropped bath back to the wall.
The same stop applies if you picked a bathroom cartridge for a frame because it was white. Five checks cover the job: cut out the old silicone, degrease and dry, fill the bath, tool while the paste is wet, and keep water off for the stated cure.
Common questions
Do you fill the bath before you seal it?
Yes. Fill it to a normal level and leave the water in until the bead has cured. An empty bath sits higher, and the first fill splits a bead gunned on that high rim. Soudal and UK fitter guides say this. It is practice, not a clause in BS EN 15651.
Can you silicone over the old bead?
You can, and it fails along the seam. Old silicone, especially a bead that is black inside, has to be cut out. White spirit cleans the film that is left. It does not replace the cut. New paste does not bond reliably to cured silicone.
How soon can you shower?
Wait for the cure the listing states, and not less than about 24 hours if it states nothing. UniBond's 20 minutes is touch dry, not shower time. The Soudal six-pack's 7 minutes is initial hardening, with 24 hours beside it. A deep bead can still be soft inside after a day.
What if the skin has already formed?
Leave it or cut it out. Pressing a skinned bead smears a torn line. On a hot day the Soudal three-pack reviews say you cannot pause. Pull the masking tape at once, and redo any section that dulled before you tooled it.
What do you clean the joint with?
Cut the old bead out first. Then white spirit, and let it evaporate so you are not sealing onto wet solvent. Soap and loose dust stop the new paste wetting the rim. A remover can soften a film. It still needs the bulk cut out.
When should you stop and call someone?
Stop if the bath or tray has dropped, if water is already under it, if the gap is too wide for a bead, or if the surround is natural stone and no sheet allows it. A cartridge will not reset a bath that has pulled off its cradle. Get the movement fixed, then seal it.
Related pages
Sources
Public UK sources used for this comparison. amazon.co.uk prices, stars and review counts were taken from the listings on 21 October 2026.
- BSI, BS EN 15651-3:2017 sanitary sealants (retrieved 21 October 2026)
- GOV.UK construction products regulation in Great Britain (retrieved 21 October 2026)
- GOV.UK acetic acid general information (retrieved 21 October 2026)
- Sika Everbuild Everflex 500 bath and sanitary silicone (retrieved 21 October 2026)
- Sika Everflex 500 EN 15651-3 declaration of performance (retrieved 21 October 2026)
- DOWSIL 785 sanitary acetoxy silicone technical data sheet (retrieved 21 October 2026)
- Bostik SX Contractors LMN silicone technical data sheet (retrieved 21 October 2026)
- UniBond Triple Protection technical data sheet (retrieved 21 October 2026)
- Soudal UK, acetoxy and neutral silicones (retrieved 21 October 2026)
- Soudal UK, painting over silicone sealant (retrieved 21 October 2026)
- Screwfix, how to silicone a shower (retrieved 21 October 2026)
- Toolstation sealant buying guide (retrieved 21 October 2026)