Leaking Shower Repair
How do you fix a leaking shower?
If showering leaves the bathroom floor wetter than the shower recess, the seal between the screen and the tiles has failed. The fix is to cut the old silicone out, clean and dry the join properly, mask both sides, and lay a fresh bead of a wet area silicone — and with Selleys No Mould you can be back using the shower within an hour of finishing.
It is an hour of work plus curing. The part that decides whether it lasts is not the bead itself but what you do before you lay it: every trace of the old silicone has to come out, and the join has to be genuinely dry. Silicone does not bond to silicone residue, and it does not bond to a damp surface.
What you need
- Selleys No Mould, or Selleys Wet Area Silicone
- A caulking gun
- Selleys Sealant Remover
- A roll of masking tape or painters tape
- Mineral turpentine
- Methylated spirits
- A soft clean cloth
- A blade or knife, or a sealant remover tool
- A spatula, and some soapy water
Step 1 — Cut the old sealant out
Remove the old sealant by pushing the knife deep inside the join and running it down the length of the seal. The sealant should peel away in long pieces, exposing the join.
Work steadily along the length rather than picking at it in short stabs — long strips come away far more cleanly and leave less behind. If it is difficult to remove, use Selleys Sealant Remover, following the instructions on the pack.
Sealant Remover's own directions are: scrape or cut the old sealant back to a thin layer less than 5 mm deep, spread at least a 5 mm thick layer of remover evenly over it with a scraper or brush, leave it for at least 10 minutes, then work a scraper or sealant remover tool backwards and forwards to lift the softened sealant off. A second application is sometimes needed on thicker beads. Clean residue and tools immediately with mineral turpentine.
It is suitable on ceramic tiles, porcelain, glass, grout, most metals, brass, laminate, most plastics, masonry, coated timber and most painted surfaces. It is not suitable for rubber, EPDM or polycarbonate, so keep it off a plastic shower base or screen seal you are not certain about, and test compatibility before use.
Step 2 — Clean the join back to bare surface
Use a cloth soaked in mineral turpentine to clean the newly exposed join area, making sure all traces of the silicone have been removed, then wipe the area dry.
Selleys' preparation advice for this job goes one step further: clean and dry the surfaces of oil, dirt and grease with mineral turpentine and then methylated spirits, and allow to dry completely before applying silicone. The two solvents do different jobs — turps lifts the silicone residue and oils, metho carries off what the turps leaves behind and flashes off without a film.
Do not rush the drying. A shower corner holds moisture long after it looks dry. Ventilate the room, put a fan on it if you have one, and come back to it.
Step 3 — Mask both sides
Protect the glass screen from silicone with a strip of tape running down its length, without covering the join itself. Do the same on the tile side of the wall.
Masking is the difference between a bead that looks professional and one that looks like a repair. It takes two minutes and it removes the need for any wiping later.
Step 4 — Load the gun and cut the nozzle
Cut the cartridge tip and place the cartridge in the caulking gun. Attach the nozzle and snip it at a 45 degree angle, sized to the width of the join. Cut it smaller than you think — you can always widen the opening, but you cannot make it smaller again.
If you have not used a caulking gun before, see how to use a caulking gun. One tip worth taking from it: when first applying product, extrude a small amount onto a piece of scrap material to make sure you have a smooth continuous flow before you start on the join.
Step 5 — Run the bead
Pump the gun until the silicone just begins to emerge, then apply evenly to the join in a downwards motion, starting from the top of the shower screen.
Work in one continuous pass, holding steady pressure and moving at an even speed, and push the sealant into the joint rather than laying it on the surface. A bead that merely sits on top has almost no depth of bond and will peel; one pressed into the gap grips both faces. Work in sections you can complete before the sealant skins.
Step 6 — Tool the bead
Use a spatula dipped in soapy water — the rounded corner — to clean up uneven areas and to make sure the silicone is worked deeply into the join. Wash the spatula in soapy water between touch-ups. A spatula dipped in mineral turps, or in detergent and water, works equally well.
Tooling does two jobs at once: it forces the sealant properly into the joint, and it leaves a smooth concave face that sheds water instead of holding it.
Step 7 — Pull the tape and clean up
Remove the tape from the wall and screen immediately after smoothing the sealant, then clean up the area with a cloth dampened with mineral turps. You have about 5 minutes to do this before the silicone begins to skin. Pull the tape once the surface has begun to set and it will drag the bead edge with it.
Step 8 — Curing, and when you can shower again
This depends entirely on which product you used, and the difference is large.
Selleys No Mould will have a firm skin and be waterproof and shower ready 1 hour after application. That is what its Speed Seal technology delivers, and it is the reason to choose it if the household has one bathroom. The semi-cured sealant must not be touched until fully cured — at least 48 hours. Using the shower is fine; poking the bead to see if it is set is not.
Selleys Wet Area Silicone should be allowed to fully cure — 72 hours — before returning the shower to use.
| Selleys No Mould | Selleys Wet Area Silicone | |
|---|---|---|
| Technology | Acetic cure silicone | Neutral cure, 100% silicone |
| Shower ready | 1 hour after application | After full cure |
| Full cure | At least 48 hours | 72 hours |
| Skin time | 20 minutes | Tool within 5–10 minutes |
| Cure rate | 2 mm / 24 hours | — |
| Joint movement capability | ±25% (ISO 9047) | — |
| Elongation | Approx. 400% (ASTM D412 modified) | 450% (ASTM D412) |
| Packaging | 290 mL cartridge, 100 mL tube; transparent or white | 420 g cartridge, matt white |
Indicative data only, not intended for the preparation of specifications.
What "2 mm per 24 hours" means for your bead
Silicone cures from the outside inwards. The 1 hour figure for No Mould is the point at which the skin is firm enough to keep water out — it is not full cure. Underneath, the material is still curing at roughly 2 mm a day, which is why the 48 hour figure exists and why a thicker bead takes longer than a thin one. Showering does not disturb the bead; touching, wiping or scrubbing it does.
Which product for which shower
No Mould is an acetic cure silicone. Acetic cure suits glazed ceramic tile, glass and porcelain — the materials a standard shower recess is made of — and No Mould is designed for humid, damp environments where mould is normally present.
Wet Area Silicone is neutral cure. Reach for a neutral cure product where the joint touches anything the acid released during acetic curing could affect — a mirror edge, natural or engineered stone. Its listed substrates include ceramic, glazed and porcelain fixtures, metal, copper and brass fittings, powder coated aluminium, aluminium, plastic laminates, rubber, glass, stainless steel and concrete.
If there is mould in the join
Black spotting in a bead is a colony rooted into the silicone, not surface dirt, which is why scrubbing never restores it. Before applying new sealant, Selleys recommends spraying Selleys Rapid Mould Killer into the gap to kill any residual mould, then drying the area thoroughly. Patch test first — staining can occur on some matt finish tiles or in hard water areas, and it is not suitable for fabric, mirror tiles, metallic surfaces, or older baths and basins.
If mould is a recurring problem across the whole bathroom rather than in one join, see black mould removal.
Limitations — where these products should not be used
- No Mould is not paintable. Complete painting 7 days before applying the sealant.
- No Mould is not suitable for aquariums, for food and drinking water contact, for permanent water immersion, or for metals other than aluminium and stainless steel.
- Wet Area Silicone is not paintable, not suitable for PP, PE or PTFE, not for aquariums, not for food or drinking water contact, and not for permanent water immersion.
- Sealant Remover is not suitable for rubber, EPDM or polycarbonate, may affect some surfaces, and should not be left on porous materials or acrylic-painted surfaces for extended periods. It will not remove staining caused by old penetrated silicone oils.
- Do not seal over an existing bead. A new layer may not adhere well to the old silicone, and an established mould colony can penetrate a new seal even where the new product contains mould inhibitors.
Keeping the new seal working
Both products are explicit about this in their own directions: the sealant must be cleaned regularly to avoid build-up of soap scum and dirt, because those are what encourage mould growth. The silicone is not the food source — the residue on it is. Running the exhaust fan and wiping the screen down after showering does more for the life of the bead than any product upgrade.
For storage, leave the nozzle screwed onto the cartridge with a little product squeezed out of the end. It cures into a plug you can pull out next time.
Common questions about fixing a leaking shower
How soon can I use the shower after resealing?
One hour with Selleys No Mould. With Selleys Wet Area Silicone, wait for full cure at 72 hours.
When is it fully cured?
No Mould needs at least 48 hours, even though it is shower ready in one. Wet Area Silicone cures in 72 hours.
Can I lay a new bead over the old one?
No. It may not adhere well to the original silicone, and any mould left underneath will come through.
How long do I have to smooth the bead?
Tool it straight away, and pull the tape within about 5 minutes before the silicone begins to skin. No Mould's published skin time is 20 minutes; Wet Area Silicone should be tooled within 5–10 minutes.
What if the leak is not at the screen?
Check the join between the tray and the wall, and around the waste and taps. The same method applies to any of those joins. For a basin or sink, see how to seal a sink.
Does a hair dryer speed up the cure?
No. These silicones cure by reacting with atmospheric moisture, so warm dry air does not help. Ventilation at normal room humidity is what you want.
How do I get the last film of old silicone off?
Selleys Sealant Remover, then mineral turpentine, then methylated spirits on a clean cloth. See how to remove old sealant for the detail.
Which colour should I use?
No Mould is available transparent or white in a 290 mL cartridge or a 100 mL tube. Wet Area Silicone is matt white in a 420 g cartridge.
Do I need a cartridge or will a tube do?
A single shower screen join is within reach of a 100 mL tube, but a cartridge in a gun gives far better control of a long continuous bead. If you are doing the tray join as well, use a cartridge.
The mould keeps coming back — is the sealant faulty?
Usually not. Recurring mould points either to residue from the previous colony left in the join, or to a bathroom that stays damp. Cut the bead out fully, treat with Rapid Mould Killer, dry thoroughly, and improve ventilation.
Can I use one of these products on a stone hob or stone shower base?
Use the neutral cure product for stone. Wet Area Silicone is neutral cure; No Mould is acetic cure.
What products are needed to fix a leaking shower according to Selleys?
Selleys recommends Selleys Wet Area (Silicone), Selleys Wet Area Speed Seal, a Selleys Light Speed Caulking Gun, and Selleys Silicone Remover to fix a leaking shower.
What tools are needed to fix a leaking shower?
The tools needed are a roll of masking tape or painter's tape, mineral turpentine, a soft clean cloth, a blade or knife, and a spatula.
How do you remove the old sealant before repairing a leaky shower?
Remove the old sealant by pushing the knife deep inside the join and running it down the length of the seal so it peels away in long pieces, exposing the join. If it's difficult to remove, use Selleys Silicone Remover following the pack instructions.
How should the joint area be cleaned after removing old sealant?
Use a cloth soaked in mineral turpentine to clean the newly exposed join area, making sure all traces of silicone are removed, then wipe the area dry.
How do you protect the glass screen and tiles when applying new sealant?
Apply a strip of masking or painter's tape down the length of the glass screen without covering the join, and do the same on the tile side of the wall to protect both surfaces from silicone.
How should the new silicone sealant be applied to the shower join?
Cut the Selleys Wet Area Silicone cartridge tip, place it in the caulking gun, attach the nozzle, and snip the nozzle at a 45 degree angle. Pump the gun until silicone begins to emerge, then apply it evenly to the join in a downward motion starting from the top of the shower screen.
How do you smooth and clean up the silicone after applying it?
Use a spatula dipped in soapy water (round corner) to clean up uneven areas and press the silicone deeply into the join, washing the spatula between touch-ups. Remove the tape from the wall and screen immediately after smoothing, then clean the area with a cloth dampened with mineral turps—there's about 5 minutes before the silicone begins to skin.
How long does it take for Selleys Wet Area Speed Seal to be shower-ready compared to Selleys Wet Area Silicone?
Selleys Wet Area Speed Seal forms a firm skin and becomes waterproof and shower-ready just 1 hour after application, though the semi-cured sealant must not be touched until fully cured after 48 hours. Selleys Wet Area Silicone, by contrast, should be allowed to fully cure for 72 hours before the shower is returned to use.
What materials is Selleys Wet Area Silicone Sealant suitable for use on?
According to the knowledge base, Selleys Wet Area Silicone Sealant works well on ceramic, glazed and porcelain fixtures, metal, copper and brass fittings, aluminium, plastic laminates, rubber, glass, stainless steel, and concrete.
Is there a faster-curing alternative sealant for mould-prone shower areas?
Yes, according to the knowledge base, Selleys No Mould Silicone Sealant is designed for mould resistance and produces a shower-ready seal in just 1 hour, compared to the standard 72-hour cure time.