Black or split silicone around your bath or shower: how to replace it

Check the seal, then check what is happening behind it.

The answer in 2 lines. Small surface marks on an intact seal may respond to appropriate cleaning. Split, missing or detached silicone needs attention because water can pass behind the bath or shower tray. Persistent staining may justify replacement, but black colour alone does not establish how deeply mould has penetrated. Before resealing, check for a moving bath, loose tiles or damp behind the joint. Remove the failed seal, prepare and dry the surfaces, and follow the sealant instructions, especially before wetting it again.

The first steps

Inspect without pulling: look for gaps, cracks and edges separating from the bath, tray or wall. Photograph the condition before cleaning.
Check nearby surfaces: look for damp skirting, loose tiles, softened flooring or a stain below. Stop using the affected shower if water is escaping.
If you rent: report the failed seal and any damp to your landlord, with photographs, before removing the silicone.

Stop: danger

Sagging or bulging ceiling below: keep everyone out of the affected room and arrange urgent assessment. Do not puncture the ceiling.
Water reaching electrics: do not touch wet switches, sockets or appliances. Keep clear and arrange urgent help.
Extensive mould or damaged backing: stop the cosmetic repair and have the moisture source and affected materials assessed.

Clean it or replace it?

A flexible, firmly attached seal with minor surface mould can be cleaned with a suitable product, following its label. Wear appropriate protection and ventilate the room. Never mix cleaning products. Persistent marks after cleaning are a reason to consider replacement, rather than repeatedly using harsher chemicals.

Missing sections, splits and detached edges need repair. If the bath or tray moves, or tiles and backing are damaged, deal with that first. Read the government damp and mould guidance, particularly its removal and prevention sections, to understand why cleaning alone cannot resolve an ongoing moisture problem.

Replacing a straightforward failed seal

Only proceed if the surrounding surfaces are sound and you can follow the bath, tray and sealant instructions. Choose sanitary silicone compatible with the surfaces involved. Read the preparation, ventilation, protection and curing requirements before starting.

Remove the failed bead and remaining residue carefully. A suitable plastic removal tool helps avoid scratching vulnerable surfaces; take particular care with acrylic.
Clean the exposed joint using a compatible method. Do not choose a solvent simply because it removes silicone: it may damage the finish.
Allow the joint to dry thoroughly. Damp backing needs investigation rather than concealment.
For a bath, follow its instructions about loading it with water during sealing. Do not assume every installation has the same requirement.
Apply a continuous bead and finish it as directed, making contact with both sides of the joint.
Keep the seal dry until the product permits water exposure. A surface skin does not necessarily mean it is ready for a shower.

What not to do

Covering a failed or mouldy bead with fresh silicone instead of preparing the joint.
Using rigid filler or ordinary decorating caulk where a suitable flexible sanitary seal is needed.
Assuming a newly sealed edge proves that the waste pipe, tray or hidden waterproofing is sound.

Help the repair last

Use the bathroom's ventilation and wipe away lingering water where practical. Clean with products suitable for the surfaces and sealant. If the extractor is ineffective, report or repair the ventilation problem rather than relying on more cleaning.

Inspect the joint as part of normal bathroom cleaning. Repeated separation suggests movement or poor adhesion that needs assessment. There is no guaranteed service life or universal curing period: preparation, installation and the chosen product matter.

Who pays, and what about insurance?

Do not assume resealing is always a tenant's responsibility. Report the defect and ask for a written decision based on its cause and your tenancy. The GOV.UK repairs guidance explains responsibilities for sanitary fittings and tenant repairs.

Local housing arrangements illustrate why checking matters: Reading's council repairs handbook lists bath sealant as a council repair. Its list applies to its own homes; use your landlord's equivalent policy for your address.

If water damage has occurred, notify your insurer promptly through your policy's claims contact. Ask what evidence to retain and what work it authorises. Cover, exclusions, excesses and reporting requirements depend on the policy; resealing does not guarantee reimbursement.

Good to know

Keep photographs before removal and after completion, along with the sealant instructions and any repair invoice.
Persistent damp after resealing needs a fresh investigation, not another layer of silicone.
This guide covers England. Tenancy responsibilities and enforcement arrangements differ in Wales, Scotland and Northern Ireland.

Illustrative example: in Reading, Elodie notices a gap at the corner of her bath. She photographs it and reports it to her council landlord. The repair includes checking the bath is stable before renewing the seal. She waits for the advised curing period before using the shower, then watches for any returning damp.

A made-up story, for illustration.

Bobby

Sources, verification, confidence

Verified on 4 November 2026, for England. Confidence: high for the need to address underlying damp, report rental defects and check local repair responsibilities; medium for the general resealing outline, which requires the installation and product instructions. Insurance cover is policy-specific. No universal curing time, replacement interval or insurance reporting deadline is asserted.