How To Repair Loose Pool Tiles
How do you re-stick a loose pool tile without draining the pool?
If tiles on the bottom or side of your pool are coming off, you do not have to drain the pool to fix them. Selleys MarineFlex can be applied — and will cure — under water. Clean the tile and the substrate, apply the product to the tile, press it into place and wipe the excess off with a cloth before it skins.
The whole repair takes a few minutes per tile. What takes longer is the cure, and that is the part to plan around: MarineFlex cures at approximately 2 mm per 24 hours, faster when submerged, and it should not be subjected to water pressure or movement until fully cured.
What you need
- Selleys MarineFlex
- A high thrust caulking gun
- A clean cloth
- Secateurs (to cut the nozzle)
The high thrust gun is not a luxury. MarineFlex is a high-viscosity sealant, and a light-duty gun will not extrude it cleanly — particularly with your arms in the water.
How to repair the tiles
- Clean the tiles. Make sure they are clean and free of oil, grease, dirt or dust. The product can be applied to wet surfaces and under water, so there is no need to drain the pool.
- Prepare the cartridge. Cut the MarineFlex cartridge tip, fit the nozzle and cut it to size, then insert it into the caulking gun.
- Apply the product to the tile, position it in place and press down firmly so the adhesive spreads across the back of the tile.
- Remove excess product with a cloth if you are under water, or with a soapy solution above the waterline, before skinning occurs.
Preparation details that make the difference
Beyond "clean", the MarineFlex data sheet gives two specific preparation steps. Plastic surfaces should be lightly sanded before application to enhance adhesive strength, and metal and plastic surfaces should be wiped over with a solvent such as mineral turps to remove all traces of oil and mould release residue from the fabrication process. For a pool, the relevant note is that fibreglass, gelcoat, polycarbonate and Perspex should be lightly sanded and wiped with turps before the product is applied — do that above water where you can.
Ceramic tiles themselves need no primer. Neither do aluminium, galvanised steel, fibreglass/FRP, gelcoat, polycarbonate, glass or most plastics (pre-test before use). Timber and concrete can only be bonded when they are sealed, primed and painted.
What the figures mean for a pool repair
| Technology | Sil-X |
| Packaging | 410 g cartridge, white or black |
| Skin formation | Approx. 40 minutes |
| Curing rate | Approx. 2 mm / 24 hours |
| Service temperature in water | 0°C to 40°C continual exposure; 40°C to 70°C short term |
| Shrinkage | 0% |
| Slump | <1 mm |
| Hardness | 75 (Shore A) |
| Elongation at break | Up to 30% |
Indicative data only, not intended for preparation of specifications.
Skin formation at approximately 40 minutes is your cleaning-up window, and it is shorter under water — the data sheet notes shorter skin formation and faster cure in wet conditions and submersion. Wipe the squeeze-out as you go rather than doing all the tiles and then cleaning up.
Zero shrinkage and slump under 1 mm are why the tile stays where you put it. A sealant that slumps would let a tile slide down the wall while you were setting the next one; one that shrinks would pull away from the edges as it cured.
A service temperature of 0°C to 40°C for continual exposure in water covers any Australian pool comfortably. Spa water in the 40–70°C range is short-term exposure only.
Elongation of up to 30% tells you this is a firm, high-modulus product rather than a stretchy one — right for a rigid tile bonded to a rigid shell, but not a high-movement joint sealant.
Limitations — read these before you start
- Not suitable for polypropylene, polyethylene or PTFE.
- Not for permanent water immersion or plugging leaks subject to pressure. This limitation sits alongside the product's ability to cure under water, and the way to reconcile the two is the guarantee: MarineFlex's 10-year watertight guarantee applies to above the water-line applications only. A re-stuck decorative tile below the waterline is a repair you keep an eye on, not one you can forget about.
- Critical seals and repairs under water should be regularly checked and repaired if required. Build the check into your normal pool maintenance.
- Not for polycarbonate and Perspex under water. Both are fine above the waterline once lightly sanded and wiped with turps.
- Cannot be used on chlorinated rubber-based pool paint. If your pool is painted, find out what with before you start.
- Cannot be used to repair flexible vinyl pool liners or inflatable pools.
- Avoid subjecting the repair to water pressure or movement until fully cured.
Clean up and storage
Clean up uncured MarineFlex with rags wetted with mineral turps. Cured sealant has to be removed by scraping or sanding. Store the cartridge in cool, dry conditions below 30°C, and use it within 6 months of opening — shelf life unopened is 12 months.
Common questions about repairing pool tiles
Do I have to drain the pool?
No. MarineFlex can be applied to wet surfaces and under water, and it will cure under water.
Does the tile need to be dry?
No, but it does need to be clean and free of oil, grease, dirt and dust.
How long before the repair is cured?
The curing rate is approximately 2 mm per 24 hours, and it is faster in wet conditions and submersion. Avoid water pressure or movement on the repair until it is fully cured.
How do I clean up the excess under water?
With a cloth, before skinning occurs. Above water, use a soapy solution.
Will it stick to my fibreglass pool?
Fibreglass and gelcoat are listed surfaces that need no primer, but should be lightly sanded and wiped with turps before application.
What about a painted pool?
MarineFlex can be applied to fully dried alkyd enamel, oil-based, water-based and epoxy paints including epoxy pool paints, but it cannot be used on chlorinated rubber-based pool paint. Confirm adhesion on a small sample first.
Can I use it on a vinyl-lined or inflatable pool?
No. The product cannot be used to repair flexible vinyl pool liners or inflatable pools.
Is the repair permanent?
Treat an underwater repair as one to inspect. The data sheet lists permanent water immersion among the product's limitations and asks that critical underwater seals be checked regularly and repaired if required. The 10-year watertight guarantee covers above-waterline applications only.
Will it work in a heated pool or spa?
Service temperature in water is 0°C to 40°C for continual exposure, with 40°C to 70°C as short-term exposure only.
What gun do I need?
A high thrust caulking gun. The product is high viscosity and a standard gun makes hard work of it.
Can I use MarineFlex on the pool coping or surrounds?
Above the waterline it suits ceramic tile, glass, aluminium, galvanised steel and most plastics without a primer, and sealed, primed and painted timber and concrete. That is also where the 10-year guarantee applies.
What else is MarineFlex used for?
Sealing leaks in boats above and below the waterline. See how to seal a leak in a boat.
What product does Selleys recommend for repairing loose pool tiles?
Selleys recommends Selleys Marine Flex for repairing loose pool tiles, as it is a high-performance adhesive sealant that can be applied and will cure even underwater.
Do I need to drain my pool to fix loose tiles with Marine Flex?
No, draining is not required. Selleys Marine Flex can be applied to wet surfaces and underwater, so there is no need to drain the pool before repairing loose tiles.
What tools are needed to repair loose pool tiles with Marine Flex?
You need a high thrust caulking gun, a clean cloth, and secateurs to complete the pool tile repair with Selleys Marine Flex.
How long does the pool tile repair process take?
The total time for the pool tile repair process is approximately 60 minutes (PT60M).
What are the steps to repair loose pool tiles using Marine Flex?
First, ensure the tiles are clean and free of oil, grease, dirt or dust (this can be done on wet or underwater surfaces). Next, cut the Selleys Marine Flex cartridge tip, fit the nozzle, cut it to size, and insert it into the caulking gun. Then apply the product to the tile, position it in place, and press down firmly. Finally, remove excess product with a cloth (if underwater) or a soapy solution before skinning occurs.
How should excess Marine Flex be removed after applying it to a pool tile?
Excess product should be removed with a clean cloth if working underwater, or with a soapy solution before the product begins to skin over.
Is a primer needed before applying Marine Flex to ceramic pool tiles?
No, Marine Flex is formulated to work on ceramic tiles without requiring a primer, making it suitable for direct application to pool tiles.
Can Marine Flex be used both above and below the waterline?
Yes, according to the knowledge-base context, Marine Flex is formally suitable for both above and below waterline applications on pool surfaces.
How should surfaces be prepared before repairing loose pool tiles?
The tile surface should be thoroughly cleaned and prepared by removing any loose or deteriorated material, and it should be clean, dry, and free from debris, algae, and old adhesive residue before applying the adhesive.
How should Marine Flex be stored, and how long can it be used after opening?
Marine Flex should be stored in cool, dry conditions below 30°C and used within 6 months of opening.