How to Build Natural Swimming Pools

Co-authored by Rob Litman

Last Updated: February 22, 2024 Fact Checked

Natural swimming pools are a great way to take a dip without swimming in chemicals. They use plants and other natural details to filter the water and keep the ecosystem of the pool balanced. They also tend to attract wildlife, making them a good spot to relax and enjoy nature. With just a few steps and some solid planning, you can build your own natural swimming pool.

Part 1

Part 1 of 4:

Digging the Pool

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1
Pick a spot that has even ground and lots of shade. Avoid a spot with tree stumps or shrubs that you will have to move. A shady spot will ensure the pool is not exposed to direct sunlight. Sun can encourage algae to grow in your natural pool, forcing your filtration system to work overtime to keep the water clean and clear.^{[1]
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- Look into your local regulations before you start any construction. For instance, in California, your pool needs to be at least 5 ft (1.5 m) away from the property line.
- View a diagram of a natural swimming pool: here.
2
Section out a hole for the pool. The hole should be at least 45 to 50 square metres (480 to 540 sq ft) and 1 to 2 metres (3.3 to 6.6 ft) deep. Try not to make the pool too deep, as a deeper pool may require steel reinforcements. Make the pool a square or rectangle so it is easy to line and fill.^{[2]
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- Use tape or chalk to mark out the dimensions of the pool so you have a guideline for when you dig.
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3
Create an adjacent hole for the plant zone. The hole should be 10 to 20 square metres (110 to 220 sq ft) and 1 metre (3.3 ft) deep. This hole is for the plants and other natural elements that will help to filter the water in the pool. It should be right beside the larger hole for the pool.^{[3]
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- The hole for the plants should take up or be equivalent to 30-50% of the main pool area.
- The plant zone will be separated from the pool by a piece of black liner that you will put in later. This will allow the water to flow from the plant zone into the pool, but keep the plants from floating into the pool area.
4
Dig the holes with an excavator. Using an excavator will make digging the holes much easier and faster. Dig the holes so they have sloped sides, as this will ensure they do not cave in. The holes should also have an even, flat bottom so sealing and filling them are easier to do.^{[4]
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- Save any large rocks that you come across as you dig, as you can use them later when you seal and fill the pool.
- You can rent an excavator from your local hardware store at an hourly or daily rate. Digging the holes should take no more than a few hours.

Part 2

Part 2 of 4:

Putting in the Water Filtration System

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1
Place a small water pump on the far end of the pool. Though the natural pool will use plants to filter the water, you will need a pump to move the water towards the plants. Buy a small water pump at your local hardware store or online. Place it at the far end of the pool and run electricity to the pump so it can run.^{[5]
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- You can bury the water pump in the ground if you do not want it to be seen.
- Running a water pump in or around water can be dangerous, so exercise caution when you set it up and make sure the wire you use is water safe. When in doubt, consider hiring an electrician to set up the water pump for you.
2
Run PVC tubing from the pump to the plant zone. Bury the tubing at least 18 inches (46 cm) deep in the soil as you run it from the pump to the hole for the plants. Run the PVC tubing underground beneath the entire pool from the far end to the plant zone. Make sure the piping touches the plant zone so the water flows into this area.^{[6]
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- If you are unsure of how to do this, you can hire a plumber or a contractor to assist you.
3
Attach an underwater aerator to the pump to add oxygen to the water. Aerating the water will ensure the water has enough oxygen to feed the plants and other organisms in the pool. Place the aerator in the deepest part or corner of the pool so it is not disturbed. Make sure the aerator is properly connected to the water pump.^{[7]
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- Underwater aerators can range in price from $1,000-$1,200 USD.
Place the pump and aerator in a plastic container or bucket with a skimmer. Then, cover the bucket with a steel-mesh filter mat to keep debris out of the equipment.^{[8]
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Part 3

Part 3 of 4:

Sealing and Filling the Pool

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1
Use synthetic liner to smooth out the bottom and sides of the pool. Place the liner tight to the bottom and sides of the pool. Cut the liner to fit the sides correctly, making sure it sits right at the top line of the pool. Line both the main pool and the hole for the water zone so they are protected.
- The synthetic liner is a good way to prevent leaks or cracks in the pool due to rocks or other objects.
2
Apply bentonite clay if you do not want to use a synthetic liner. Another option is to apply a layer of bentonite clay over the holes for the swimming pool and the plant zone. You will need at least 6 pounds (2.7 kg) of clay per square foot to seal the pool. Spread a 2 to 3 inches (5.1 to 7.6 cm) layer of clay with your hands. Wear gloves and a face mask to protect yourself.^{[9]
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- If the soil is very sandy, you may need to double the amount of clay per square foot to ensure the pool is properly sealed.
- Pack the clay down with a tractor or a plate compactor to really seal it into the soil.
3
Lay black liner on the bottom and sides of the pool to reflect the sun. Use synthetic liner that is black over the base liner or the clay so it can trap the heat of the sun, heating up the pool naturally. It will also help to protect the pool from leaking.^{[10]
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- Leave a piece of liner hanging between the pool and the plant zone. Cut the piece so it sits 1 to 2 inches (2.5 to 5.1 cm) below the top edge of the pool. This piece of liner will act as a barrier between the pool and the plant zone.
- Use scissors to cut the liner so it just drapes over the sides of the pool.
4
Place large rocks on the walls of the pool to keep the liner in place. Use smooth slabs or rocks to secure the liner and create an extra barrier. Lay them against the walls of the pool so they sit flush to the top edge of the pool. You can then fill in any gaps between the large rocks with smaller rocks or slabs.^{[11]
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- You can also use stone slabs that have been cut to fit together if you want a smooth, even surface for the sides of the pool. The stone slabs will be heavy to lift so you may need someone to help you lift them in place.
5
Fill the pool with 4 to 5 inches (10 to 13 cm) of gravel or pea rock. Cover the bottom of the pool with gravel or pea rock to create a good habitat for microorganisms. This will also keep the bottom soft and easy to walk on.^{[12]
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- Make sure you use gravel or pea rock that has been washed so there is no dust or particles in the pool.
6
Line the edge of the pool with rocks or pebbles. Finish off the pool by placing small rocks or pebbles on the edge so they cover up the black liner. Make sure the liner is completely covered and there is a clear perimeter around the edge of the pool with the rocks. Reinforce the rocks with gravel and soil so there are no leaks.^{[13]
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- Make sure there is a clear pathway between the pool and the plant zone, as water will need to flow between these 2 areas.
7
Put water in the pool and let it rest for a week. Use fresh water to fill the pool to the top edge. Then, let it sit and monitor the pool for any leaks or issues. Test the water with a home water testing kit to ensure the pool levels are safe and not contaminated with any chemicals or biological substances.^{[14]
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- Do not fill the plant zone until you are ready to add plants to the pool.

Part 4

Part 4 of 4:

Adding Plants

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Use aggregate or gravel that does not contain any additives or large portions of organic matter that has not decomposed. Make sure the aggregate has not been in contact with animals, as you do not want germs or bacteria to get into the water.^{[15]
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2
Fill the plant zone with water 1 foot (0.30 m) below the top edge. Use fresh water to fill the plant zone. Make sure the water runs into the pool area easily so the plants can help to filter the water.^{[16]
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- Check that the piece of black liner you are using as a barrier sits upward in the water, preventing the plants from drifting into the pool area.
Waterweed and hornwort are both great options, as they release a lot of oxygen into the water. You can also put in aquatic plants like sedges and rushes on the perimeter of the plant zone to keep the area oxygenated and contained.^{[17]
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Water lilies and other floating plants are great options for the plant zone, as they encourage the growth of microorganisms that will keep the water healthy and clean.^{[18]
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If you are using plants that have roots, shovel gravel onto the bottom of the plants so they stay in place in the plant zone.^{[19]
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Community Q&A

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Question

Is it possible to add fish?

Community Answer

Yes, but make sure that the fish are compatible with the plants and temperature of water.

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Question

Will the water turn green from the plants? If so, is that bad?

Community Answer

That is very unlikely, but if the water does turn green, don't use the pool. it could mean chemicals or algae have contaminated the water.

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Question

How does square footage translate to length and width for the pool and plant zone?

Community Answer

The dimensions aren't very precise. Using 22-foot sides gives you a 484 square foot "pool". A a 5-foot-deep shelf (in this configuration) gives you a 27' by 27' complete pool size with approximately one third plant zone.

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