These gorgeous people, Douglas Buege and Vicky Uhland, explain how to build a natural swimming pool on your own estate. The tutorial includes tips on pool zoning, sealing the pool, natural filtration, algae control, and maintenance.
Advantages of the natural pool are:
- A natural pool can be constructed for as little as $2,000 if you do it yourself, while conventional pools can cost tens of thousands of dollars!
- Natural swimming pools require no harmful chemicals, are fairly low-tech, and once established call for only a modicum of management.
- You won’t have to drain the pool each autumn. Except for topping it off now and then, you’ll fill the pool only once.
Dig a natural swimming pool by hand
The cheapest and most ecologically sound way to build a swimming pool is simply to dig a hole in the ground. You can make your pool as shallow or as deep as you want, but the key is to ensure the sides slope: Otherwise the soil will cave in. The ratio should be a 1-foot vertical drop for every 3 horizontal feet. “It’s not a bathtub effect, but more like a soup bowl,” says Tom Zingaro, partner with Denver-based Blue Lotus Designs, a pool-and pond-architecture company. One of the main reasons traditional swimming pools are constructed with a steel framework is to ensure the walls stay vertical and perpendicular to the bottom surface of the pool. Construct a pool with sloping sides and you will eliminate the need for any steel reinforcement.
2. Zoning your pool
Reserving at least 50% of your pool’s surface area for shallow plants, either at one end or in a ring around the sides, eliminates the need for chlorine and expensive filters and pumps. You’ll need to separate the swimming area of your pool and the filtration area, or plant zone.
A rim within an inch of the water’s surface keeps plants in their place but allows water from the swimming area to move to the plant zone for filtering, As water passes through the fibrous root structure of the plants, bacteria concentrated on the plants’ roots act as a biological filter, removing contaminants and excess nutrients in the water. Decomposer organisms, also found in the plants’ root zones, consume the bacteria, effectively eliminating underwater waste accumulation.
Inside the plant zone, the water should get steadily deeper, reaching a maximum depth of 18 inches near the swimming zone. The outermost 6 inches of the plant zone will be 2 to 3 inches deep, providing a habitat for taller aquatic plants. Submerging and floating vegetation occupy the deeper area.
Water lilies (Nymphaea) adapt to any depth, so use them liberally. Floaters, such as pondweeds and common duckweed, drift freely on the surface and quickly cover the surface of the plant zone. Besides cleaning the water they will make your pool beautiful to behold!
Sealing your pool
You have a couple of options, depending on your soil conditions, to ensure the pool holds water.
You can apply either:
- a layer of bentonite clay to seal the soil or
- lay a synthetic liner.
Bentonite is usually the cheaper option, averaging 35 cents per square foot. Liners can cost 25 cents to $1 per square foot, depending on their composition and weight.
Bentonite works as glue, bonding with the soil particles and preventing pool water from seeping into the ground. Some soils may contain enough clay that simply compressing the pond bottom will enable it to hold water. Talk to local pond builders to find out for sure. But beware: Bentonite doesn’t bond well with sandy soil. Particularly sandy soil can require up to 12 pounds of bentonite per square foot, as opposed to 6 pounds in clay-rich soil.
Bentonite also can be troublesome when the surrounding soil is very dry. In arid climates, Zingaro recommends bentonite to be applied beneath a plastic liner that is woven or textured on the bottom. This liner keeps the bentonite from shifting. In more humid climates, bentonite can be applied directly to the soil. Before treating your pool with bentonite or any other clay powder, thoroughly compact the soil. You can do this with a lawn roller or a plate compactor. Then, while wearing a mask, spread a 2- to 3-inch layer of bentonite powder along the pool sides and bottom. Pack it down with a tractor or plate compactor. Then apply another foot of quality topsoil and compact again.
If you opt for a liner, select one made of ethylene propylene diene monomer rather than PVC. EPDM is a synthetic rubber twice as expensive as PVC, but it’s worth the extra cost. It has protection from ultraviolet rays, and unlike PVC remains flexible in cold weather. If your soil has a lot of rocks or roots, select a 45- or 60-millimeter liner. You can use a 30-millimeter liner if your soil is very sandy and smooth, and if you and your guests aren’t likely to tear holes in a liner while frolicking in the pool. Before laying your liner, compact the sod and cover it with a layer of sand or an absorbent material such as old carpeting or newspaper. Newspaper is a good option: When wet, it bonds to the liner, providing extra protection if the liner develops a small hole.
4. Natural pool filtration
The water needs to circulate continuously for the plants’ roots to cleanse the pool. You may also need to aerate the water so that oxygen is supplied to the water organisms. Without adequate oxygen, your pool water could become stagnant, harboring stinky anaerobic bacteria!
Water can be channeled from your pump into your plant zone through the use of PVC tubes. Zingaro recommends using flexible PVC in cold climates. In any climate, bury the tubing in the soil about 18 inches deep. Underwater aeration, which uses less energy than constructed waterfalls and circulates water more effectively, involves diffusing air at the pool’s bottom. You can also build your own aerator, using an air compressor (1/4-horsepower for a pool smaller than an acre) and high-strength tubing that connects to a diffuser. The diffuser which bubbles air through the water, rests in the deepest part of the pool, where swimmers are not likely to damage it. Expect to pay $1,000 to $1,200 for a quality underwater aeration system.
How to control algae in your pool
Pond owners have been battling algae the mighty green menace — for eons. Algae compete with plants for nutrients and light, but spring algae blooms often decline as soon as water lilies and other plants emerge to shade the water. Promote plant growth and deter algae by adding plants and eliminating phosphorous to maintain a lower pH (5.5 to 6.5).
The easiest remedy, and the least risky to your aquatic ecosystem, is to add more plants, which will out-compete the algae for nutrients. A second option is to monitor the pool for phosphorus. Fertilizers and urine are the two major sources of this nutrient, so ensure that your pool is free of nutrient-rich runoff – just remind everyone to use the toilet before swimming!
Enzymes, bacteria, acids and other strange brews have been offered as magic “bullets” for persistent algae. Introducing additives to your pool may be an interesting scientific experiment, but it won’t necessarily improve the pool you’ve invested plenty of time and money in. Beware of salesmen hawking their grand variety of miracle algae cure-alls. Remember: Your pool is a dynamic, living natural ecosystem. Adding chemicals will not bring it back into balance.
Natural pool maintenance
Removing plant litter in spring and fall will help maintain a long life of your natural pool. Keep your water level constant, and be prepared to add water as needed. Cheap test kits, available in garden centers, will allow you to monitor your pool’s nutrient levels, alerting you to problems.
In addition to maintaining the pool’s biological health, check the mechanical systems annually. Wipe diffusers with vinegar to remove deposits, check air hoses for cracks and obstructions, and examine all connections to the pumps.
When you have a swimming pool, you and your family are able to not only have fun, but get fit in a way in which it doesn’t really feel like exercising!
So create and enjoy your own cooling retreat for this and upcoming summers!