Hot tubs are becoming increasingly popular. They offer the opportunity to relax in your own garden. Most hot tubs are made of wood. Wood insulates well and also adds atmosphere to the garden. Because wood insulates well, the water remains warm for a long time and not too much energy or wood is needed to heat the hot tub.
The hot tub remains waterproof as long as there is water in it. However, this water must be changed regularly. Hot tubs are often emptied, after which the wood will dry and shrink and the hot tub will leak.
We receive a lot of questions about how you can make the hot tub waterproof again with vinyl ester resin or epoxy. On this information page we take you step by step through the process of lining the inside of your hot tub with vinyl ester resin or epoxy resin. The covering can easily be applied by a handy do-it-yourselfer.
In this article we discuss two ways to waterproof your hot tub. For example, you can waterproof the hot tub using vinylester resin or with epoxy resin. In the diagram below you can see the most important properties of vinylester resin and epoxy resin.
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We recommend using vinylester resin because it is especially suitable for hot tubs. In addition, vinylester is resistant to hot water and chemicals such as acids and chlorine.
Clean the hot tub properly. Brush the wood thoroughly and sand the wood. Plan the work in advance and prepare the materials. Start with the walls and then the bottom. Let the bottom rise 10 centimetres against the walls.
After you have thoroughly cleaned the hot tub, you can apply the bonding primer to ensure good adhesion between the wood and the vinyl ester resin. The G4 adhesion primer consists of 1 component. This means you do not have to mix the polyurethane resin with a hardener, so you can apply the resin directly to the wood of the hot tub with a flat brush or fleece roller. Depending on the circumstances, this G4 primer will be sufficiently hardened after 30 minutes to 2 hours so that you can continue with the vinylester resin.
Once you have applied the primer and the wood has good adhesion, you can start laminating with vinylester resin in combination with fibreglass.
Mix the vinylester resin with approximately 2% hardener. Weigh this carefully and mix the two components well for optimal results. Moisten the surface with vinylester resin and place the fibreglass mat in it.
Wet the mat with a fleece roller. The mat will become transparent and supple. Use the flexibility to fold the mat around difficult parts. If there are still white spots, more resin should be applied there. Avoid shiny spots, the structure of the mat must remain visible.
After each layer you need to deaerate the whole thing with a deaerator roller. This will cause the laminate to slightly darken in colour, so you can see where you left off.
A second layer can be laminated immediately after the first layer (wet on wet). You must also ventilate this layer well. You can now let it harden completely.
Clean the surface with acetone and lightly sand it with 60 grit sandpaper. This is how you remove raised fibres. After sanding and degreasing, apply a layer of polyester gelcoat. Add approximately 2% MEKP hardener to the base and mix well. Then apply a layer of gelcoat with a fleece roller.
Gelcoat cures adhesively, so that it has optimal adhesion with the next layer of polyester topcoat.
In the last step you finish the hot tub with a polyester topcoat. Gelcoat hardens adhesively, so you can apply the topcoat without sanding or degreasing. With a layer of gelcoat and topcoat you have a nice thick layer that protects the hot tub well.
Topcoat is easy to use. Add sufficient hardener to the base (2.5-3% at 15℃, 2-2.5% at 20℃, 1.5-2% at 25℃) and mix well. Then apply a layer of topcoat with a fleece roller.
Let the topcoat harden for about two days. After the topcoat has hardened, you can fill the hot tub with water again!
Clean the hot tub thoroughly. Brush the wood thoroughly and sand the wood. Plan the work in advance and prepare the materials. Start with the walls and then the bottom. Let the bottom rise 10 centimetres against the walls.
After you have cleaned the hot tub thoroughly, you will impregnate the hot tub with epoxy resin.
Mix the transparent epoxy coating thoroughly with the supplied hardener in the correct mixing ratio (100:60), do not forget to scrape along the bottom and edges of the mixing cup!
Apply the epoxy resin to the inside of the hot tub with a roller and let this layer harden.
After curing, the wood will still feel rough. Therefore, lightly sand the wood until it is smooth again. You can now move on to the next step.
If the wood has a first layer of epoxy coating, you can start laminating with epoxy in combination with glass fibre.
Mix the epoxy resin with the supplied hardener in the correct mixing ratio. Weigh this carefully for optimal results.
Moisten the surface with epoxy resin and place the glass fibre mat in it. Wet the mat with a fleece roller or velour roller. The fibre will become transparent. If there are still white spots, more resin should be applied there. Avoid shiny spots, the structure of the fibre must remain visible.
After each layer you need to deaerate the whole thing with a deaerator roller. This will cause the laminate to slightly darken the colour, so you can see where you left off.
A second layer can be laminated immediately after the first layer (wet on wet). You must also ventilate this layer well. You can now let it harden completely.
After the laminate has hardened, you can lightly sand the fibreglass epoxy with 60 grit sandpaper. This way you remove any raised fibres.
Now apply a final layer of transparent epoxy coating. Mix the base component with the hardener and apply it thinly with a roller.
After half a day, apply another layer and let this coating harden for 7 days. You can now fill the hot tub again!
First of all, you need to know the dimensions of the hot tub. Measure the height and diameter of the hot tub. With these dimensions the surface area of the wall and the surface area of the bottom can be calculated:
The wall: multiply the diametre in metres by 3.14 (pi) and multiply this by the height in metres. This number is the surface area of the wall.
The bottom: divide the diametre in metres by 2. Multiply this number by itself (suppose the result is 1.5, then also multiply by 1.5). Multiply the result by 3.14 (pi). The result is the surface area of the bottom. Add the surface area of the wall and bottom together. Please charge extra for overlapping and loss.
Then a few things may have gone wrong:
Temperature too cold: was the temperature at least 15℃ during processing? If not, you should wait longer or try to warm it up a little. If you added too little hardener, you can try the same.
Did you forget the hardener? If you forgot to add the hardener, all you have to do is take it all out and start over.
In the article above you could read how you can make your hot tub waterproof again in two ways. Do you have any questions about the products or working methods or do you need advice? Our specialists are happy to share their professional knowledge with you! Contact them here for questions, advice or a no-obligation quote.
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