Swimming is a quintessential summer activity, offering both relaxation and recreation. Imagine enjoying a refreshing dip in your own backyard oasis, built with natural materials and free of harsh chemicals. This guide will walk you through building your own natural swimming pool, a beautiful and ecologically sound alternative to conventional pools.
While gaining popularity, natural swimming pools (NSPs) are still relatively new in many regions. Unlike traditional pools that rely on concrete, fiberglass, chlorine, and energy-intensive filtration systems, NSPs utilize gravel, stone, clay, and aquatic plants to create a balanced and self-sustaining ecosystem. This approach results in a stunning, environmentally friendly pool that’s also cost-effective.
Why Choose a Natural Swimming Pool?
Natural swimming pools offer several advantages:
- No Harmful Chemicals: NSPs eliminate the need for chlorine and other chemicals, creating a healthier swimming environment.
- Low-Tech and Sustainable: Relying on natural processes reduces energy consumption and minimizes environmental impact.
- Ecologically Diverse: Aquatic plants oxygenate the water, support beneficial bacteria, and provide habitat for frogs, dragonflies, and other wildlife.
- Cost-Effective: With DIY construction, NSPs can be significantly cheaper than traditional pools.
- Aesthetically Pleasing: NSPs blend seamlessly into the natural landscape, creating a beautiful and relaxing outdoor space.
Planning Your Natural Swimming Pool
Digging the Pool
The most affordable and eco-friendly way to begin is by excavating a hole in the ground. You can customize the depth and size, but it’s crucial to slope the sides to prevent soil collapse. A recommended ratio is a 1-foot vertical drop for every 3 horizontal feet, creating a “soup bowl” effect rather than a bathtub. This sloping design eliminates the need for steel reinforcement typically required in conventional pools.
Zoning and Filtration
A key element of NSPs is the separation of the swimming area and the plant zone, which acts as a natural filter. Allocate at least 50% of the pool’s surface area to shallow plants, either at one end or surrounding the perimeter. A submerged rim, positioned just below the water surface, keeps plants contained while allowing water to circulate between the zones. As water flows through the plant zone, bacteria on the plant roots act as a biological filter, removing contaminants and excess nutrients. Decomposer organisms further break down waste, preventing buildup.
Within the plant zone, create varying depths, with the outermost 6 inches being 2-3 inches deep for taller aquatic plants and the remaining area reaching a maximum depth of 18 inches near the swimming zone. This shallow plant zone not only purifies the water but also warms it quickly and provides habitat for beneficial insects like mosquito larvae-eating frogs.
Natural Pool Filtration System
Continuous water circulation is essential for the plant zone to effectively cleanse the pool. Aeration is also important to ensure sufficient oxygen levels for the aquatic organisms.
Water can be channeled to the plant zone using PVC tubes buried about 18 inches deep. Underwater aeration is an efficient method, using an air compressor and diffuser to bubble air at the bottom of the pool. A 1/4-horsepower compressor is sufficient for pools smaller than an acre. Aerate the pool for 4-8 hours daily, ideally in the morning and evening. Protect the aerator, pump, and skimmer by placing them in a plastic container with a steel-mesh filter mat. Expect to invest $1,000-$1,200 for a quality underwater aeration system.
Skimmers can be added to remove floating debris like leaves, preventing algae growth. Running electrical devices near water requires careful planning; always connect electrical hardware through a buried conduit and consult a qualified electrician.
Sealing and Lining Your Natural Swimming Pool
After digging, you have a few options to ensure your pool holds water.
- Bentonite Clay: Bentonite is a cost-effective option (around 35 cents per square foot) that acts as a natural sealant. It bonds with soil particles, preventing water seepage. However, it’s less effective in sandy soil. In arid climates, consider using bentonite beneath a plastic liner.
- Synthetic Liner: Liners range from 25 cents to $1 per square foot, depending on the material. Opt for an EPDM (ethylene propylene diene monomer) liner, as it’s UV-resistant and remains flexible in cold weather. Choose a thicker liner (45- or 60-millimeter) for rocky soil and a thinner one (30-millimeter) for sandy soil. Before laying the liner, compact the soil and cover it with sand or absorbent material like old carpeting or newspaper.
After installing the clay or liner, cover the bottom of the pool with 4-5 inches of clean gravel to provide habitat for beneficial bacteria. In addition to the lining, consider adding cobblestone steps for easy access.
Building a Natural Pool Construction with Concrete
For those who prefer a more traditional pool shape, concrete or Rastra blocks (made from cement and recycled foam plastic) can be used. While less eco-friendly than natural materials, these options still reduce chemical and energy use when combined with plant-based filtration systems.
Pouring concrete requires expertise to prevent cracking. A 4-1 ratio mix of portland cement and sand is recommended. Cover the compacted soil with fiber mesh, a rubber liner, old carpeting, or newspaper for a stable surface. Apply a 1/8-inch coat of stucco to waterproof the concrete.
Alternatively, Rastra blocks are lightweight and easy to install. Secure the blocks to a concrete slab or rubber liner with rebar and fill the cavities with concrete. Waterproof the blocks with two coats of stucco and backfill the space between the pool and the blocks with soil. Finish the perimeter with stones or plants.
Planting and Soil Preparation
Before planting, prepare the plant zone with 3-6 inches of soil. Select soil that is free of organic matter and contaminants. Have soil samples tested for potentially pathogenic bacteria. Avoid soil from areas with animal excrement. After adding soil, gravel, and hardware, fill the pool, disturb the soil as little as possible and allow it to rest for a week before planting.
Selecting Plants for your Natural Swimming Pool
Choose plants suited to your climate. Native-plant suppliers are the best source for aquatic plants. Sedges (Carex) and rushes (Scirpus) are excellent emergent vegetation for the pool’s perimeter. Consider lesser cattails (Typha angustifolia) and aquatic irises, selecting varieties that won’t overcrowd other plants. Pickerel weed (Pontederia cordata), arrowhead (Sagittaria), and water primroses (Ludwigia) thrive in shallow areas. Include submergent plants like common waterweed (Elodea) and hornwort (Ceratophyllum) for their high oxygen output. In deeper areas, plant a mix of floating, submergent, and emergent plants. Water lilies (Nymphaea) adapt to any depth, and floaters like pondweeds (Potamogeton) and common duckweed (Lemna minor) quickly cover the surface.
Avoid collecting plants from the wild to preserve the wetlands. Instead, consider rescuing plants from threatened sites. Once you have your plants, group them according to height and type, anchoring them in the soil with plenty of gravel.
Algae Control
Algae compete with plants for nutrients and light. Promote plant growth and deter algae by adding more plants and eliminating phosphorus to maintain a lower pH (5.5 to 6.5). Avoid nutrient-rich runoff and remind swimmers to use the bathroom before entering the pool. Increase aeration to stimulate biological activity. Avoid introducing synthetic chemicals or miracle algae cure-alls, as they can disrupt the pool’s ecosystem.
Natural Pool Maintenance
Regular maintenance will ensure the longevity of your NSP. Remove plant litter in spring and fall. Maintain a constant water level and monitor nutrient levels with test kits. Annually check mechanical systems, wipe diffusers with vinegar, check air hoses, and examine pump connections.
Natural Pool Safety
The probability of contracting a serious disease from a natural swimming pool is low. However, aquatic plants do not remove all contaminants, and pools constructed of dirt, concrete, or rubber liners do not necessarily keep bacteria at bay. Keep babies and pets out of the water to avoid fecal coliform contamination. Have the water tested if you are concerned about water quality.
Building your Natural Swimming Pool
Building a natural swimming pool is a rewarding project that connects you with nature and provides a healthy and beautiful swimming experience. By following these guidelines, you can create a sustainable and enjoyable backyard oasis for years to come.
