How to build a natural swimming pool

As you see in the table of contents, we will first discuss what a natural swimming pool is and why it is beneficial, before we dive into how to build it.

The advantage of having a pool

It sure sounds pleasant to have a pool. One that you can dip into when you want, – any time of the day or the night. One you can sit by with your friends and family on a hot summer day and just chill. For most of us this will remain a distant dream. Mostly because of the cost. A pool is expensive to build and certainly expensive to maintain. In addition, it may or it may not have occurred to you, but added to the economical cost of building and maintaining a conventional pool, comes a big environmental impact. In many areas water is not an abundant resource and a family pool of about 12×24 ft (3.5x6m) holds about 10,000 gallons (38 000 liters) of water.

As water evaporates plus the fact that many of the pools end up leaking into the grown, the pool needs to be topped up regularly. A pool like the mentioned family pool could loose around 8,000 gallons (30 000 liters) of water per year due to evaporation only, depending on where you live of course.

Click to see the earth current water situation... -infographic

​Another thing is that it is not only the water that evaporates, so does many of the chemicals you put into it. These includes, but are not limited to chlorides and cyanuric acid. It is also a worrying thought that chemicals will also be absorbed by the body when swimming in the pool.


Did you know?

The evaporation can be reduced with up to 97% by using a pool cover.

A solar cover can even help you heat your pool!

Mark Scholz

Good bang for the buck

Good bang for the buck. Sturdy enough to use for winter cover. I use a pool cover roller with it and can manage by myself. Recommend cutting it to size to help keep debris out of pool. Btw you need a sharp razor to cut it or some darn good scissors.

This video shows how easily your body absorbs chlorine from water

How does chlorine disinfect?

It works much like boiling does. Inside the bacteria are lots of protein molecules that are essential to the bacterias life. The chlorine (commonly known as bleach) causes these to clump together, much like the egg whites in a boiled egg. The problem is that the chlorine cannot not distinguish between the good and the bad bacteria so it will kill both.

Have you noticed how well bleach works on stained white clothes, but how it will weaken the fiber over time. Chances are it will do something similar to the body tissue.

A pool for 3000$

But over to the good news: It actually is possible to be environmentally responsible and own a pool. You can minimize the impact by going for smaller splash pools, you can also go for a chemical free pool, or you can build a natural pool that not only gives you a pond to swim in, it actually gives back to the environment with its symbiotic relationship between plants and bugs, water and oxygen. And if you already own a conventional pool you can convert it to a chemical free pool or to a natural pool.  A natural swimming pool is relatively low maintance, plus if you build it yourself you can get a descent size pool for as little as 3000$!

Does that sound interesting? Well, then read on!

​Lets take a look at some key elements to building a natural pool. Remember, there is no “one size fits all” when it comes to natural pools. Do the proper research on your soil, on the materials you want to use, take into consideration the climate where you live and how you are going to use the pool. Research what water plants are native to your area and also check out nearby ponds and lakes to see real proof of what kind of water plants thrive there.

What is a natural swimming pool?

A natural swimming pool is not a saltwater pool. A natural pool does not make use of chemical for maintaining the water, but instead uses natures own tools like plants, invertebrates etc. A natural pool will usually be divided in two zones, one for swimming and a shallower regeneration zone filled with plants. The regeneration area can be on one end of the pool or in a ring around the swimming area. This area should at least be 50% or your pools surface. A brim up-to about an inch from the water surface will keep the plants within the regeneration area. The plants will filter the water through their roots and in the process remove the contaminants and bacteria.

A natural swimming pool will need some sort of pump to aerate the water and softly move it from one zone to the other so that all of it can be cleaned. You can use a conventional pool pump, but you can also use a big aquarium type pump. Check out David Pagan Butlers DVD to see how that is done.

Building a natural pool

A pool, natural or not, still requires a huge amount of water, so and will in most cases also need to be topped due to evaporation. You can buy water for your pool from dedicated companies as you may not be allowed to fill it up with regular tap water. We will come back to this later.​

Plan out the space

When you plan for a natural pool, the best option is probably to go for vinyl lining or you get a fiberglass pool. In any case you will have to add from 50% up to a 100% of the swimming area of the pool to allow for an area for a planted zone.
In other words, if you plan for a family sized pool of 12×24 ft (3.5x6m), you should at least have a zone half that size for regeneration area. The space requirements for a pool certainly is much bigger than for a conventional pool, the on the positive side, the bigger the planted area, the lower maintenance and the more users it allows for.

Digging out and shaping the pool

You probably know the soil already, but if you don’t you certainly need to know it before you start digging. Having much clay in the soil is perhaps not something one is usually happy about, but in this case you can use it to your advantage. If it is very sandy, it will have a tendency to collapse so you need to take that into account.

When it comes to shaping the pool, you can go for the conventional box shape with straight angular sides. The downside here is that the building expense will be a bit higher as you will need cement and/or ICF (Insulated Concrete Forms) blocks and you may even need help from professionals as laying the cement for a pool can be a bit tricky. The positive side of this choice however is that it is less likely to suffer under tearage with use

The most economical shape for a pool is the soup bowl shape, were the pool slopes gradually from shallow to deep. The optimal slope is about 35 degrees. This design will not give problems with dirt walls caving in.

When you have determined how big you want your pool, draw it up on the ground in the spot you intend to put it.

Dig the whole about 6 ft bigger to allow for insulation if your geographic area requires that. Remember insulation is to keep the heat in the water. If it gets very hot in your area you may not want to insulate. You may want the heat to seep into the ground underneath the pool. Because if the water gets too hot the plants and the wildlife may suffer and you have potential algae problem. Depending on what kind of pump/aeration system you are going to use, you may at this point want to dig in tubes for the pump underground.

Dig the regeneration zone in a slope from the edge of dry land until it meets the swimming area. Usually starting at 2 inches (5cm) and sloping until about 18 inches (45cm), where you will place the brim to hold the plants in. This is because different plants and wildlife, like frogs, salamanders and invertebrates thrive in different depths of water. Frogs and salamanders are excellent allies for you as the clean your water plus they eat the mosquito larvae.

You will need to seal the pool in some way or the water will just seep down in the ground and disappear. Again you have different options. If you would like to go all the way ecologically and if your soil allows it, you could opt for Sepp Holtzers version and use no lining. His method would be, very briefly explained, to dig the hole for the pool and then fill it with a couple of inches of water and then use the back of the excavator to pond down the soil to compact it. This will make the different parts of soil separate into separate layers, where the clay would go down as it is the smallest the particles and the stones would rise up as they are the biggest. If you go for this option you need to be very thorough as any un-compacted area would let the water seep through and into the ground beneath.

Other faster and more reliable methods would be to use Bentonite clay or an synthetic liner, or a combination of the two. Bentonite however, is not a good option if your soil is very dry or high in sand as it will not bind very well to dry matters.

When it comes to liners, we again have a variety of choices. You should however make your choice carefully. EPDM is a material recommended by many and it is a resistant material offering a very good performance. It has ultraviolet protection and will not become brittle in cold winters. In any case it is a very good idea to put a layer of protection between the soil and the liner. Wet newspapers are excellent for this… but perhaps not as easy to get your hands on any longer.

Prepare the pool bottom

When the liner or the clay is properly installed, cover the pool with a gravel. About 5 inches or so. This provides substrate for the beneficial bacteria. It is very important that the gravel is clean. Perform a test by putting gravel in a bucket and fill it with water. If it is not clean, then find another supplier. If you go for the sloped kind of swimming area, you may want to create a platform with a ladder or stairs to make it easier to get in and out of the water without damaging the lining. This is, as you see the downside of using the cheaper approach and go for the sloped sides.

Prepare for the planting

When your pool structure is finished you should fill the regeneration zone with 4-6 inches of soil for the plants. Choose the soil with care. It should not contain any organic matter or fertilizer or any excrements. Good composted clean soil is good. When the plant zone prepared and the water and aeration pumps installed you can fill the pool with water. But let the it all sit for a week or so before adding the plants.

Choose the water

It may not be allowed to fill pools with municipal tap water from the hose. You should check with you water company first if you plan to go that way, or you may be in for an unpleasant surprise, often in form of a hefty fine. You could also go for well water or rain harvested water. If none of these options are available to you you can order water and get it delivered to you on a truck. Just do a Google-search for bulk water delivery and the name of your area.

If you choose this option you would want to make sure that your pool is not filled at maximum pressure as these trucks can fill a regular pool in about 10 minutes. However this kind of water pressure may damage and/or wrinkle the lining in your natural pool.

Fill the regeneration zone with local water plants and enjoy your pool without worrying about chemicals.

Do you worry your natural pool will be filled with mosquitos?

Watch this video and you will stop worrying.

Here a couple of really good resources to help you planning and maintaining your natural pool:

"They mean it when they call this a 'complete how to guide'. It answered all my questions and then some... Mick was even able to double check everything before we got started so we could be sure we got it right!" - Homeowner, Texas

Pros: His homemade bubbler system is easy, cheap, and wouldn't injure any wildlife. Kudos!!! Good thinking!

Simply put this book is a MUST READ for anyone intersted in any aspect of Sustainable and Ecological Design. It should be read right along with Permaculture by Mollison, the Passive Solar Handbook by Mazria, Rainwater Harvesting by Lancaster, and ecocities to Living Machines by Todd. Even if you aren't specifically interested in making a swimming pool (which you will be after reading it) the insights into the workings of hydro-ecologies and how to design natural systems are invaluable!