Imagine a swimming pool that doesn’t smell of chlorine. One that feels more like a refreshing dip in a mountain lake, surrounded by lush aquatic plants. That’s the promise of a natural swimming pool—or biopool, if you prefer. Honestly, it’s more than just a pool; it’s a living, breathing ecosystem in your own backyard.
Here’s the deal: instead of relying on harsh chemicals, these pools use natural processes to keep the water crystal clear. It’s a blend of old-world wisdom and modern engineering. And the result? A stunning, sustainable feature that’s as good for the environment as it is for your peace of mind. Let’s dive into how they work and, crucially, how they’re built.
How Does a Natural Pool Even Stay Clean?
It’s the first question everyone asks. If there’s no chlorine, what stops it from turning into a murky green pond? The secret lies in separation and regeneration. A typical biopool design splits the area into two distinct zones:
- The Swimming Zone: This is your classic, deep-end, swimming area. It’s for laps, play, and relaxation.
- The Regeneration Zone: This is the shallow, planted area. It’s the pool’s biological filter, packed with specific aquatic plants and a substrate like gravel or lava rock.
Water is constantly circulated—gently, you know—from the swimming area through this regeneration zone. The plant roots and the beneficial microbes that colonize the gravel bed work together as a natural water purification system. They consume nutrients that would otherwise feed algae, they break down organic matter, and they oxygenate the water. It’s a beautifully simple, closed-loop system.
Core Biopool Construction Methods: Two Main Paths
When it comes to construction, there are two primary methods. Your choice will depend on budget, site conditions, and the aesthetic you’re after. Both methods, of course, require careful planning and, usually, professional help.
1. The Liner-Based System
This is often the more cost-effective and quicker route. Think of it like a sophisticated, heavy-duty pond liner. After excavating the shape—swimming zone and regeneration zone included—a protective geotextile fabric is laid down. Then, a flexible, reinforced PVC or EPDM rubber liner is installed to create the waterproof basin.
The regeneration zone is then filled with a specific substrate (like washed gravel) and planted. The edges are often finished with natural stone, timber, or even a planted shelf to blend seamlessly into the landscape. It’s versatile and allows for more organic, free-form shapes.
2. The Concrete or Shotcrete Method
For a more permanent, rigid structure, concrete is the go-to. This method involves building a steel-reinforced concrete shell, often sprayed on (shotcrete) for strength and to conform to complex shapes. It’s incredibly durable and allows for precise, geometric designs if that’s your style.
The key difference here is the need for a specialist waterproof coating. Standard pool plaster won’t do; it can leach chemicals. Instead, you’d use a natural, inert coating like a clay-based product (like bentonite) or a specific mineral render that’s safe for the ecosystem. The regeneration zone is then built within this concrete shell, partitioned off but hydraulically connected.
Key Components You Can’t Skip
Beyond the shell or liner, a few non-negotiable systems make the whole thing tick. Forget these, and you’ve just got a fancy pond.
- The Circulation Pump: This is the heart. It needs to be sized correctly to move the entire volume of water through the regeneration zone at least once every 12-24 hours. And it should be energy-efficient—this thing runs constantly during the swimming season.
- The Skimmer and Bottom Drain: These are the workhorses that remove surface debris (leaves, pollen) and heavier sediment before it can decompose and overload the system.
- The Substrate in the Regeneration Zone: This isn’t just dirt. It’s a carefully selected, porous medium like lava rock or specific gravel. Its huge surface area is where the magic happens—home to billions of water-cleansing bacteria.
- The Plant Selection: Not just any pretty reed will do. You need a mix of oxygenators (like hornwort), emergent plants (like iris or cattail), and floating plants. Each plays a specific role in the nutrient cycle.
The Build Process: A Rough Timeline
So, what does building a natural swimming pool actually look like on the ground? Well, it’s a dance of heavy machinery and delicate planting. Here’s a simplified breakdown:
| Phase | Key Activities | What’s Happening |
| 1. Design & Excavation | Finalizing shape, depth, zones. Major digging. | This sets the entire stage. Getting the slopes and levels right for the two zones is critical. |
| 2. Shell Construction | Liner installation OR concrete forming/shooting. | Creating the waterproof vessel. This phase feels the most like traditional pool building. |
| 3. Mechanical Install | Plumbing pipes, pumps, drains, electrical. | The hidden nervous system goes in. Everything must be accessible for maintenance. |
| 4. Regeneration Zone Build | Adding substrate, planting aquatic flora. | The artistry begins. This is where the pool gets its “living” character and filtration power. |
| 5. Filling & Start-Up | Initial fill with water, system commissioning. | Water goes in, pumps turn on. Then, the hardest part: waiting. The ecosystem needs weeks to establish and clear. |
That start-up period is crucial, by the way. The water will often go through an algae bloom—it’s a rite of passage—before the plants and bacteria balance out and it becomes sparkling clear. Patience is not just a virtue; it’s a requirement.
Honest Pros and Cons: Is a Biopool Right for You?
It’s not all serene swims and dragonflies. Natural pools come with their own set of realities. Let’s weigh them.
- The Upsides: No red eyes, no bleached swimsuits, no chemical smell. Your skin and hair will thank you. The biodiversity is incredible—you’re creating a habitat. Operating costs are lower long-term (no chemical purchases). And the aesthetic… it’s simply unparalleled, blending into natural landscapes in a way a blue-tiled pool never could.
- The Downsides: Higher initial construction cost, typically 20-30% more than a conventional pool. They require more space for the regeneration zone (it should be at least equal in surface area to the swim zone). You’ll need to do some basic “gardening”—pruning plants, removing debris. And in some climates, they have a shorter swimming season; the water warms more slowly and cools faster without a heater.
That said, the trend is toward more sustainable, chemical-free living. For many, the trade-offs are more than worth it.
A Final, Rippling Thought
Building a natural swimming pool is a commitment. It’s a decision to work with nature, not against it. To embrace a little wildness in exchange for water that feels… alive. Sure, it asks for a different kind of attention than a traditional pool. Not better or worse, just different. More observational. More holistic.
In the end, you’re not just constructing a place to swim. You’re installing a piece of ecology. A dynamic, living system that changes with the seasons, attracts wildlife, and offers a profoundly different kind of tranquility. It’s a reminder that sometimes, the most advanced technology has been right there in the wetlands all along, quietly purifying, waiting for us to catch up.
