The natural swimming pool, explained
A natural swimming pool is a lined body of water split into two parts: a clear swimming zone and a shallow planted zone, often called the regeneration zone, where gravel, roots and bacteria take up the nutrients that algae would otherwise feed on. A small pump moves the water between the two. There is no chlorine, salt or copper, so the water feels soft and smells of nothing much at all.
In the US a natural pool typically costs $50 to $100 per square foot of total water area, so a 400 sq ft swimming zone with an equal planted zone comes to roughly $40,000 to $80,000.
How the water stays clean without chlorine
A chlorinated pool kills almost everything in the water. A natural pool works the other way round: it starves algae. Algae need nutrients, above all phosphorus, so the system is designed to keep phosphorus very low. Water is pumped from the swimming zone through the gravel of the regeneration zone, where a film of bacteria breaks down organic matter and the plants and biofilm lock up what is released. Cleaner water returns to the swimming zone.
The result is water you can see the floor through, but it is not sterile. You will see the odd water boatman, dragonfly larvae in the plant zone and a thin film on the walls that you brush off. That is the trade most owners are glad to make.
Because nothing in the water kills germs on contact, owners should test it from time to time, keep ducks and dogs out, and avoid swimming with an upset stomach, the same common sense the CDC recommends for lakes and rivers.
A natural pool suits you if
- You want to swim without chlorine or salt and are happy with water that is clean and clear, but alive.
- You have room for a planted zone roughly as large as the swimming area.
- You like the look of a pond or a landscaped water garden more than a bright blue tank.
- Your summers are warm but your water can be kept in the 70s °F with depth and some shade.
- You would rather spend weekends skimming leaves and trimming plants than balancing chemicals.
- You plan to stay in the house long enough to enjoy a garden that takes a season or two to mature.
What a natural pool costs in the US
| Item | Typical US range |
|---|---|
| 500 sq ft of water About a 250 sq ft swimming zone, for dips and short laps | $25,000 to $50,000 |
| 800 sq ft of water About 400 sq ft of swimming, the most common family size | $40,000 to $80,000 |
| 1,000 sq ft of water Room for a 30 to 35 ft swim lane | $50,000 to $100,000 |
| 1,500 sq ft of water A large pool with a deep end and a wide plant shelf | $75,000 to $150,000 |
| Permit and inspections Varies by county and city | $250 to $2,000 |
| Code-compliant barrier Fence and self-closing gates, where needed | $2,000 to $13,500 |
Typical US prices from two national cost guides published in 2025, read November 2026. National figures in US dollars, for the whole water area (swimming plus planted zone). A guide, not a quote. The cost guide gives a range for the size and system you pick.
Will it work where you live?
Natural pools were developed in Austria and Germany, where summers are warm and winters cold, and they do well across most of the northern and central US. Cold winters are no problem: the pool stays full, the plants die back, and the surface can freeze.
The challenge is heat. The warmer the water, the faster algae grow and the harder the biology has to work. In the Southeast, Gulf Coast and desert Southwest, builders tend to use more depth, more shade, a larger planted zone or a hybrid system with a biofilter. In very hot spells, warm untreated fresh water also carries a small risk from organisms such as Naegleria fowleri, which the CDC links to warm lakes and ponds; keeping water cooler and avoiding diving or getting water up the nose are the usual precautions.
Your plant list follows your USDA hardiness zone. A builder chooses native or hardy aquatic plants that will survive your winter and not spread into local waterways.
What goes into a natural pool
Excavation and shaping
The hole is dug in two levels: a swimming area typically 6 to 8 ft deep at its deepest, and a shelf of 6 to 18 in for plants around or beside it.
A sealed liner
Most US builds use a flexible EPDM or reinforced liner laid over a protective fleece, sometimes over shotcrete walls. The liner keeps the system separate from groundwater.
The dividing wall
A wall stops just below the water line between the two zones, so swimmers stay out of the gravel and plants while the water flows over the top.
The regeneration zone
Washed gravel and a mix of submerged, floating and marginal plants. Bacteria living on the gravel do most of the cleaning; the plants take up what is left.
Circulation
A low-energy pump, a skimmer to catch leaves, and pipework that draws water from the swimming zone and returns it through the gravel or a separate filter.
Edges and access
Stone, timber or concrete coping, steps or a ladder, and often a deck. These finishes are where budgets vary most.
Picturing one in your yard? Tell us where it would go.
Get a quoteHow a natural pool gets built
Site and design
The builder checks sun, trees, slope, soil and access for an excavator, then sizes the two zones and agrees the look with you.
Permits
Plans go to the building department, and in most places a barrier plan too. Allow a few weeks to a few months.
Dig, line and build
Excavation, walls, liner, pipework and the dividing wall. Most builds take several weeks on site, longer with stonework.
Fill, plant and settle
The pool is filled, planted and left to establish. Expect some cloudiness or algae in the first months while the biology settles.
Common questions
Is a natural swimming pool safe to swim in?
A well-designed and well-kept natural pool is generally clean and clear, but the water is not disinfected. Have it tested by a state-certified lab now and then; the EPA recreational water criteria for fresh water are a sensible yardstick. Keep animals out and stay out if you are ill. Our blog has more on water testing.
How big does the plant zone need to be?
For a fully plant-filtered pool, builders usually aim for a planted area about the same size as the swimming area, sometimes more in hot climates. Systems with a mechanical biofilter can work with a much smaller plant zone, or none.
Do natural pools smell or attract mosquitoes?
A healthy natural pool should smell of very little. Moving water and the insects and larvae that live in it, such as dragonfly nymphs, make it a poor place for mosquitoes to breed; the CDC advice is to deal with still, standing water, which is not what a circulating pool is.
Can a natural pool be heated?
Yes, gently. Solar heating is the usual choice and the US Department of Energy puts a solar pool heater at about $2,500 to $4,000 installed. Most designers keep water below the high 70s °F because warm water favors algae.
Does a natural pool need a fence?
In most of the US, yes. Local codes based on the International Swimming Pool and Spa Code treat any pool deeper than 24 in as needing a barrier at least 48 in high with self-closing, self-latching gates. The CPSC barrier guidelines explain the details.
How long does a natural pool last?
The liner, pump and pipework are the parts that wear. Good EPDM liners are commonly expected to last decades when protected from sun and sharp stones; pumps need replacing every several years.
Get a quote for a natural pool
Three short steps: your ZIP code, the pool you are picturing, and how to reach you. Most people finish in under two minutes.
We are an introduction service, not a natural pool builder. You hear the builder's name from us first; we hold your details back until you say they can go.
Thank you. We have your details.
- By the next working day you should hear from us, by phone or email, with a natural pool builder who builds near you.
- If you are happy with that builder, say so and we pass your notes on. If not, nothing is shared.
- The builder visits the yard and prices the design with you. We will not send you newsletters or offers.