How do you waterproof a concrete pool?

How do you waterproof a concrete pool?

Are you planning on building a concrete pool, but you have no idea how waterproofing concrete swimming pools is supposed to be done? Or maybe you have an old swimming pool under work and now it’s time to waterproof it?

Waterproofing concrete structures that contain or handle the water is essential as we know. The rebar that might be near-surface is slowly getting wet and there might be small cracks getting water slowly, but surely.

To prevent the pool from getting damaged by water, it’s only natural to waterproof it. When it comes to using different products for that, it’s important to do it right.

The waterproof product has to adhere to the concrete while the concrete has to be in a shape that it can adhere to.

I’ll try my best to describe these things so you will know at the end of this article how to waterproof a pool.

Waterproofing method for swimming pool

So how do you waterproof a pool? You will have to use a swimming pool waterproofing system to protect the concrete from water.

There are many swimming pool waterproofing products on the market. There are epoxy, polyurethane, cementitious, and some rubber products to begin with.

It’s hard to choose a coating as everything is the best since sliced bread if you believe the ads. So let us try to look a bit deeper into it.

Epoxy coating

This is usually an affordable way to coat a pool. Epoxy is a chemical and water-resistant material that becomes a hard surface when ready. Pool epoxy needs to be flexible so it can handle expanding and shrinking that happens in the pool.

Waterproof epoxy for swimming pools needs proper products used on the concrete surface before it can be coated with epoxy primer and final coat. Usually, the coatings have a product of the same series that goes well with them to be used on the concrete before primer.

That might be some sort of plaster to be used for leveling the concrete surface. So it should be a cement-based product that has something else mixed in it as well that provides more waterproofing.

Epoxy is famous for its adhering quality so it should stick to the walls and floors well.

Polyurethane coating

Epoxy and polyurethane usually go in hand in hand. Both are used pretty much in the same situations and sometimes one wins when there are situations where the other is clearly better.

Polyurethane is usually more flexible. To be honest, I don’t know if it’s so with pool products, but I assume it is. So if there are lots of expanding and shrinking it might take a win in that kind of situation.

It’s not as hard a surface as epoxy so if flexibility is taken away, epoxy wins. Both are quite chemical resistant and used in a lot of places where that is needed.

Here as well, concrete is plastered before applying polyurethane. Usually, polyurethane products use epoxy sealers as it adheres poorly to concrete. So the epoxy solves that problem as it sticks to it more than well.

Cementitious coating

The cementitious waterproofing swimming pool is a bit different process from the previous ones. It’s used a lot before tiles are installed on the pool.

It can be a two-component product like the epoxy and polyurethane coating, but it’s a cement-like powder mixed with a liquid that comes with it. It can be spread with a finishing trowel.

I’ve only used this kind of product once on an elevator pit that had to be waterproofed. The coating was almost as wet as paint, but still could be troweled on the walls.

I’m quite sure this is the same kind of method as when waterproof render for swimming pools is being used. That is a cement-like product with a liquid for it as well.

No matter which is the case, the surface can be rendered with these kinds of products or tiles can be used on top of them. The last one should be quite a traditional look for a pool.

Cementitious waterproofing swimming pool usually adheres well to concrete

Swimming pool waterproofing material facts

No matter which pool waterproofing material is chosen, it’s good to make sure that it’s a good fit for your pool. Depending on how it’s built you need to know if there is positive or negative pressure.

Positive pressure is water pushing the coating on the cement walls inside the pool. Negative pressure would be outside water pushing the coating off the concrete.

Now negative pressure can break your waterproof so you should solve that kind of problem if you have one. In the building phase, it’s easy to waterproof the exterior of the pool.

If the pool is already built, the outside wall should be opened for waterproofing to solve this. You might know you have this kind of problem if your old coating was not able to stick to the pool wall.

When you’re picking concrete pool waterproofing products you should compare how long they last and what’s the price. How often are you willing to have the pool coated etc.

Pool surfaces usually last from 5-10 years depending on the water chemistry and use. When you think it like that it might become more about aesthetics if there are no demands set by the ground it’s built on.

How to waterproof a concrete swimming pool

After going through the products, let us finally get to swimming pool waterproofing. You know a bit about the materials now so the process is easier to explain.

This will be a direction-giving step-by-step guide as the products are many. Some basic facts still remain that can be used for directions.

Step 1: Pool waterproofing should begin from inspecting the concrete. If there are cracks, they should be fixed. Check this water tank fix guide for directions on how to fix cracks that are caused by water.

Step 2: After cracks are repaired, if there is any, the walls should be made level. You have your waterproofing product at hand, it should come with instructions on what should be done before it can be coated.

So use the product it advises you to use to level the walls and floors. It might be an extra trick to get more adhering or it might be for more waterproof.

Remember to float the surface if it’s something like a rendering product. If it can be sanded, then use sandpaper on it so the next coating will look nice.

Step 3: After you’re done with making the walls and floors level or just smooth if there are curves, it’s time for the swimming pool waterproofing membrane.

Depending on the product, follow the instructions again. If it says primer, follow the primer instructions.

It’s important that you check the times as well. If it says to use a coating on primer inside a 12-hour window, do so. It means it will adhere to it better that way.

Step 4: This should be the final coating. Apply it to the primer once or twice, depending on the instructions.


I hope you got something about how to do you waterproof a concrete pool from this article. It’s important that you notice that most of the time, it’s a multiple-layer job.

There is concrete, possible leveling, using primer, coating, etc. involved. It’s important to get them all right so you have a proper waterproof surface.

More than that, it’s also important that the external conditions are right as well. Negative pressure is a serious thing that can ruin a good job done.

For that reason, I’d leave this job for professionals, if I wasn’t sure about the conditions. If you know your ground and pool, you can also DIY if you’re confident in your work.

I know I would be doing most of it by myself, just for the process of learning.

It’s also important to compare the coating systems and get them to spill some facts like how long will they last. They should be able to tell what kind of products should be used before applying the coating as well.