Convert Swimming Pool to Pond – Cost, Process & Is It Worth It?
Yes, you can convert a swimming pool into a pond. Both in-ground concrete or gunite pools and vinyl-liner pools work well as the shell for a koi pond, a planted natural pond, or a natural swimming pond. The existing hole saves you the biggest cost of a new build, excavation. Most Chicago-area conversions run roughly $8,000 to $40,000 depending on the style you choose.
That is the short answer. The real decision, and where homeowners want honest guidance, is which type of pond fits your yard, what the process actually involves, and whether conversion beats simply filling the pool in. Below is the contractor-level walkthrough we give homeowners across Cook, DuPage, Lake, Kane, Will, and the other counties we serve.
Can You Really Turn a Swimming Pool Into a Pond?
Yes, and it is one of the smartest uses for a tired pool. A swimming pool is essentially a pre-dug, structurally reinforced hole in the ground, which is exactly what a pond needs. The excavation and the retaining structure are already paid for, so you are converting an asset rather than starting from scratch.
Both major pool types convert successfully:
- Concrete and gunite pools are easiest. The rigid shell is strong and can be sealed and used as-is or lined with pond-grade EPDM rubber for a natural look and long-term waterproofing.
- Vinyl-liner pools convert well too. The old vinyl liner is usually replaced with a 45 mil EPDM pond liner over protective underlayment, which handles fish, plants, and freeze-thaw far better than pool vinyl.
- Fiberglass pools can be converted but are trickier, since the smooth shell is hard to plant into and build shelves against. These usually get a full liner and internal shelving.
The one honest caveat is depth. Most in-ground pools are 6 to 8 feet at the deep end, deeper than a koi pond needs and much deeper than a wildlife pond wants. That is not a dealbreaker. The extra depth is either an asset for koi overwintering or something you partially backfill to create planting shelves.
What Are the Main Pool-to-Pond Conversion Options?
There are three main directions for a pool to pond conversion, and picking the right one drives everything else, from cost to maintenance to how the finished feature looks. Here is how they compare.
| Conversion option | What it involves | Typical cost range |
|---|---|---|
| Koi pond | Liner or sealed shell, bottom drain, mechanical and biological filtration, aeration, skimmer, rock and gravel interior, planting shelves built up from the deep end | $15,000 to $40,000+ |
| Natural planted pond (water garden / wildlife pond) | Liner over the shell, backfilled shelves for marginal plants, gravel bottom, gentle recirculation, heavy native planting, light or no fish load | $8,000 to $25,000 |
| Natural swimming pond (NSP / swim pond) | Split design with a swimming zone and a separate planted regeneration zone, biological filtration instead of chemicals, aeration and circulation, no chlorine | $30,000 to $70,000+ |
A koi pond is the choice when you want fish as the centerpiece. Koi need good filtration, aeration, and typically 3 to 4 feet of depth minimum, so a deep pool shell is genuinely useful. This is the most equipment-heavy option and the most rewarding for hobbyists. Our guide on how to build a backyard koi pond covers what a proper koi setup needs.
A natural planted pond turns the pool into a wildlife-friendly water garden with lily pads, marginal plants, maybe a few goldfish, and frogs and dragonflies that show up on their own. It is the lowest-cost, lowest-maintenance conversion because it leans on plants instead of heavy mechanical filtration.
A natural swimming pond lets you keep swimming without chlorine. It splits the old pool into a clean swimming area and a planted regeneration zone that filters the water biologically. It is the most involved and expensive route, but it appeals to homeowners who loved swimming and hated the chemicals and running costs.
How Do You Convert a Pool Into a Pond? Step by Step
The sequence matters. Skipping the shell assessment or the filtration sizing is where conversions go wrong. Here is the process we follow on Chicago-area pool conversions.
Pool-to-Pond Conversion Checklist
- Drain the pool and cap the equipment. Pump out the water responsibly, then have the old pool pump, heater, and chlorinator disconnected. A licensed electrician should cap any pool electrical you are not reusing.
- Assess the shell. Inspect the concrete or vinyl for cracks, spalling, and structural movement. Minor cracks are fine under a liner, but major structural failure changes the plan, which is why an on-site inspection matters before you commit.
- Choose a sealed shell or a full liner. A sound gunite shell can be waterproofed and used directly, but most conversions add a 45 mil EPDM pond liner over underlayment for a natural look, better sealing, and fish safety. Vinyl-liner pools almost always get a new pond liner.
- Address the drains and plumbing. Existing main drains and skimmer ports must be sealed or repurposed. A koi pond benefits from a proper bottom drain routed to the filter, so this is the stage to plumb it.
- Build shelves and depth zones. This is the defining step. Pools are a uniform bowl, but ponds need varied depth. Backfill sections of the deep end with clean fill or stacked block to create 10 to 18 inch planting shelves, a mid zone, and a deeper zone. Keep 3 to 4 feet of depth somewhere if you want koi to overwinter.
- Install filtration and aeration. Add a mechanical and biological filter sized to the water volume. Natural ponds can use a bog or wetland filter, while koi ponds need a pump-fed filter plus a skimmer. Add an air pump and diffuser too, which keeps fish healthy, feeds beneficial bacteria, and keeps a hole open in winter ice.
- Add rock, gravel, and hardscape. Line the shelves and bottom with rounded river gravel and edge boulders. This hides the liner, houses beneficial bacteria, and gives a natural look instead of a lined bowl.
- Add a waterfall or stream if desired. A cascade or pondless waterfall add-on provides circulation, sound, and extra oxygenation, and it is one of the most popular upgrades on a conversion.
- Fill, dechlorinate, and plant. Refill with fresh water, treat out any chlorine, and plant marginals on the shelves, submerged oxygenators, and lilies in the deeper zones. Native Illinois plants establish fast and need little care.
- Cycle the system, then stock fish. Let the biological filter establish for a few weeks, then add koi or goldfish gradually so the bacteria colony can keep up with the load.
Most conversions run one to three weeks of work depending on style and weather, not counting the biological cycling time before you stock fish.
How Much Does a Swimming Pool Pond Conversion Cost?
Swimming pool pond conversion cost depends mostly on which pond type you choose, the size of the pool, the condition of the shell, and how much rock, filtration, and planting you want. The figures below are typical ranges we see across the Chicago area, not fixed quotes. Every site is different, and prices vary with shell condition and access.
| Project scope | Typical cost range | What is included |
|---|---|---|
| Basic natural planted pond | $8,000 to $15,000 | Liner over shell, shelves, gravel, basic filtration, native planting, light fish |
| Full natural / wildlife pond with waterfall | $15,000 to $25,000 | Liner, shelves, bog or wetland filter, waterfall, aeration, heavy planting |
| Koi pond conversion | $15,000 to $40,000+ | Liner, bottom drain, koi-grade filtration, skimmer, aeration, rock, planting |
| Natural swimming pond (NSP) | $30,000 to $70,000+ | Split swim and regeneration zones, biological filtration, circulation, hardscape |
A few things move the number. A cracked or failing shell needs repair before it can hold water. Poor equipment access adds labor. Koi-grade filtration and a bottom drain cost more than a simple planted-pond setup, and a waterfall raises the total but pays back in circulation and enjoyment. For a broader picture of pond pricing, our 2026 pond installation cost guide breaks down the components.
The key savings versus a brand-new pond is excavation. On a from-scratch build, digging and hauling spoil is one of the largest line items. With a conversion, that hole already exists, which is why converting a pool is often cheaper than building an equivalent pond in open lawn.
Is Converting a Pool to a Pond Worth It? Pros and Cons
Conversion is worth it when you no longer swim but do not want the cost, safety worry, or eyesore of an unused pool, and you would enjoy a low-chemical water feature instead. It is not automatically right for everyone. Here is the honest trade-off.
Pros of converting:
- Uses the existing structure. You reuse the hole and shell, avoiding the biggest excavation cost.
- Ends pool running costs. No more chlorine, no gas or electric pool heating, and far lower seasonal chemical and utility bills.
- Lower maintenance than a pool. A balanced natural pond largely self-regulates through plants and bacteria, versus constant pool chemistry.
- Wildlife and beauty. You gain fish, frogs, dragonflies, birds, and blooming plants where you had a static blue rectangle.
- Often adds appeal. A well-built water feature can be a selling point where a dated pool is a liability for many buyers.
Cons and honest cautions:
- It is still a real project, a mid-size landscape build, not a weekend swap.
- Fish and plants need care. A koi pond has real upkeep, even if it differs from pool chemistry. See what a pond cleaning and maintenance plan covers.
- You lose lap swimming unless you choose a natural swimming pond.
- Open water is still open water. A pond carries similar child and pet safety considerations to a pool, so plan edges and fencing accordingly.
If you are weighing conversion against removing the pool, it comes down to what you want the space to be. Filling in gives you flat lawn and zero water upkeep. Converting gives you a living feature for a similar or often lower cost than a full pool demolition and haul-away. If your real complaint is the pool itself and not water in the yard, conversion usually wins. If you want the water gone entirely, removal is the honest answer.
What Illinois-Specific Factors Should You Plan For?
Converting a pool in the Chicago area comes with local realities that homeowners in milder climates do not face. Get these right and the pond thrives.
Build for frost depth. Frost drives roughly 3 to 4 feet deep in our soils, and the region sees hard winter freezes. If you want koi or goldfish to overwinter outdoors, keep at least one zone 3 to 4 feet deep so the fish can settle below the ice. A deep pool shell is ideal for this.
Keep water moving in winter. A pond needs a hole kept open in the ice for gas exchange so fish do not suffocate. Run an aerator or a floating de-icer through winter, which is why we size aeration carefully on every Illinois conversion.
Plan for freeze-thaw on the shell. Concrete pools that sit empty through Chicago winters can crack from frost heave and hydrostatic pressure. An EPDM liner over the shell absorbs minor movement far better than a rigid sealed surface, one reason we usually recommend lining.
Mind drainage and the water table. Our heavy clay soils drain slowly, and a high spring water table can push on an empty or lined shell. Proper hydrostatic relief and grading keep water moving away from the structure and the house.
Check permits before you start. Rules vary by town across Cook, DuPage, Kane, Lake, McHenry, Will, Kendall, Grundy, and DeKalb counties. Some municipalities require you to officially decommission the pool, address fencing and barrier codes, or permit electrical and plumbing changes. Call your local building department first, and call JULIE 811 before any digging.
How Do You Choose the Right Conversion for Your Yard?
Start with how you use the space and how much upkeep you want. Ask yourself these questions:
- Do you want fish as the main event? If koi are the goal, plan a koi pond with proper filtration, aeration, and a deep zone. It is the most rewarding and the most hands-on.
- Do you want low maintenance and wildlife? A natural planted pond is the easiest to live with, the cheapest to build, and it fills with frogs and dragonflies on its own.
- Do you still want to swim? Only a natural swimming pond keeps swimming without chlorine, and it is the most complex build.
- What is the shell condition? A sound gunite shell keeps costs down. A cracked shell needs repair first, and our pond repair team handles that assessment. Fitting the feature into the surrounding yard matters too, and our notes on installing a custom pond in the landscape help you plan the transitions.
The best conversions start with an honest on-site assessment. Shell condition, depth, access, and your goals all shape the right plan.
Ready to Convert Your Old Pool Into a Pond?
If you have an unused or expensive-to-run swimming pool and you would rather have a koi pond, a natural planted pond, or a chemical-free swim pond, Midwest Pond Features can help you weigh the honest options for your property. We handle the whole process, from assessing the shell to filtration, planting, and stocking, and we serve Chicago and the surrounding counties, including Cook, DuPage, DeKalb, Grundy, Kane, Kendall, Lake, McHenry, and Will. Learn more about our pond installation service, then request a free quote and on-site assessment and we will give you straight answers on cost, style, and whether conversion or removal fits your yard best. Call us at [phone number] to get started.
Frequently Asked Questions
How much does it cost to convert a swimming pool into a pond?
Most Chicago-area pool to pond conversions run roughly $8,000 to $40,000. A basic natural planted pond starts around $8,000 to $15,000, a koi pond runs $15,000 to $40,000 or more, and a natural swimming pond can pass $50,000. Cost depends on pond type, pool size, shell condition, and filtration. Every site differs, so get a quote.
Can you turn any swimming pool into a koi pond?
Almost any in-ground pool converts to a koi pond. Concrete and gunite shells are easiest, vinyl-liner pools get a new EPDM pond liner, and fiberglass shells are workable with a full liner. The deep end actually helps, since koi need 3 to 4 feet of depth to overwinter safely through Illinois winters.
Is it cheaper to convert a pool or fill it in?
It depends on the pool and your goal. Filling in a pool is usually cheaper up front for a flat lawn, but a basic pond conversion can be comparable in cost while giving you a living water feature. Converting reuses the hole, avoiding excavation, which is why it often beats building an equivalent new pond.
Do koi survive winter in a converted pool pond in Illinois?
Yes, if the pond has a deep zone of 3 to 4 feet and you keep a hole open in the ice with an aerator or de-icer. Koi settle into the deep water and slow down for winter. A former pool deep end is ideal for this, since it easily provides the depth koi need to overwinter.
Do I need a permit to convert my pool to a pond in Illinois?
Often yes, since many municipalities require you to officially decommission the pool and may regulate fencing, electrical, and plumbing changes. Rules vary across Cook, DuPage, Lake, Will, and the other counties. Call your local building department before starting, and call JULIE 811 before any digging.
How long does a pool to pond conversion take?
Most conversions take one to three weeks of construction depending on the pond type, pool size, and weather, plus a few extra weeks of biological cycling before you add fish. A simple planted pond goes faster, while a koi pond or natural swimming pond with full filtration, hardscape, and a waterfall takes longer.
