Converting a Chlorine Pool to Natural: Complete UK Guide

Converting to Natural: Is It Worth It?

If you're tired of red eyes, chemical smells, and the ongoing cost of pool chemicals, converting your existing chlorinated pool to a natural swimming pool is an appealing option. Learn more about how natural pools work to understand what you're getting. But is it feasible, and does it make financial sense?

Natural Pool Excavation and Liner Installation

Why Consider Conversion?

Reasons Owners Convert

Health and wellbeing:

• Eliminate chlorine exposure for skin, respiratory, and overall health
• No more red eyes and skin irritation
• Safe if water is accidentally swallowed
• Better for children and those with sensitivities

Environmental concerns:

• No chemical runoff
• Create wildlife habitat
• Reduced environmental impact
• Lower carbon footprint

Aesthetic appeal:

• Transform stark pool into garden feature
• Year-round beauty
• Attract wildlife
• Unique property feature

Long-term savings:

• No chemical purchases (£500+/year saved)
• Lower running costs
• Reduced equipment replacement
• Less intensive maintenance

Is Your Pool Suitable for Conversion?

Ideal Candidates

Pools most suitable for conversion:

• Larger pools: 50m²+ with space for regeneration zone
• Concrete/gunite pools: Easily modified
• Pools needing refurbishment: Combine repairs with conversion
• Pools with surrounding garden space: Room for plant zones

Challenging Candidates

Conversion may be difficult or impractical for:

• Fibreglass/GRP pools: Limited modification options
• Very small pools: Insufficient space for regeneration zone
• Indoor pools: Require special considerations
• Pools with no surrounding space: Nowhere to add plant zones

Essential Space Requirements

For successful conversion, you need:

• Existing pool volume of 40m³+ (approx. 25m² at 1.6m depth)
• Additional space equal to 30-50% of pool area for regeneration zone
• OR willingness to sacrifice part of swimming area for plants

Conversion Options

Option 1: Full Natural Conversion

What's involved:

• Add separate regeneration zone
• Install biological filtration system
• Remove chemical treatment equipment
• Introduce aquatic plants
• Modify existing circulation

Space needed: Additional 30-50% of pool area

Typical cost: £35,000-£65,000

Result: True natural swimming pool with separate swim and planted zones

Option 2: Hybrid Bio-Pool Conversion

What's involved:

• Upgrade filtration to biological system
• May retain some technology assistance
• UV or minimal phosphate treatment
• Less space required than full natural

Space needed: 15-25% of pool area

Typical cost: £25,000-£45,000

Result: Significantly reduced chemicals with smaller regeneration zone

Option 3: Within-Pool Conversion

What's involved:

• Sacrifice portion of existing pool for regeneration zone
• Divide pool with submerged wall
• No additional excavation needed
• Best for large pools

Space needed: None additional

Typical cost: £30,000-£50,000

Result: Natural pool within existing footprint (but smaller swim area)

The Conversion Process

Phase 1: Assessment and Design (2-4 weeks)

1. Pool survey: Condition of shell, liner, equipment

2. Site survey: Space for regeneration zone

3. Water testing: Baseline readings

4. Design development: Regeneration zone sizing and position

5. Quotation: Detailed breakdown of works

Phase 2: Preparation (1-2 weeks)

1. Drain existing pool: Proper disposal of chlorinated water

2. Remove chemical equipment: Chlorine dosers, salt cells

3. Repair any damage: Cracks, liner issues

4. Prepare for new construction: Access, materials

Phase 3: Construction (4-8 weeks)

For separate regeneration zone:

1. Excavation for new zone

2. Liner installation

3. Aggregate substrate placement

4. Water circulation system

5. Connection to existing pool

6. Initial filling

For within-pool conversion:

1. Construct dividing wall

2. Create substrate areas

3. Modify circulation

4. Prepare planting zones

Phase 4: Biological Establishment (8-12 weeks)

1. Dechlorinate thoroughly: Multiple water changes if needed

2. Plant regeneration zone: Diverse aquatic plants

3. Introduce beneficial bacteria: Seed the system

4. Balance the system: Monitor and adjust

5. Wait for establishment: Patience is essential

Phase 5: Ready for Swimming

Once water tests confirm:

• No chlorine residue
• Stable biology
• Clear water
• Healthy plant growth

Typically 10-16 weeks from project start.

Cost Breakdown

What You'll Pay For

Factors Affecting Cost

Higher costs:

• Poor pool condition requiring repairs
• Limited access
• Rock or difficult soil
• Large pool size
• Premium finishes for regeneration zone

Lower costs:

• Good pool condition
• Easy access
• Suitable soil
• Within-pool conversion option
• Owner handling some landscaping

Comparing Conversion vs New Build

For new build costs, see our complete costs guide.

Conversion Advantages

• Lower total cost (typically 40-60% of new build)
• Faster completion
• Retain existing pool infrastructure
• Less disruption
• Maintain pool location

Conversion Limitations

• Constrained by existing pool shape/size
• May not achieve optimal proportions
• Some existing issues may persist
• Less flexibility in design—see our design ideas for inspiration

When New Build Makes Sense

• Existing pool in poor condition
• Pool very small or wrong location
• Want significantly different design
• Major garden redesign planned

Rule of thumb: If your pool needs £30,000+ in repairs anyway, consider whether new build offers better value. See our 10-year cost comparison for financial context. Not all natural pool companies handle conversions—check our guide to UK builders who specialise in pool conversion.

Maintaining Your Converted Pool

First Year

The transition period requires extra attention:

• Weekly water testing
• Monitor plant health
• Watch for algae (normal initially—see our maintenance guide for tips)
• Adjust circulation as needed
• Be patient with the system

Ongoing Maintenance

Once established, maintenance is similar to any natural pool:

• Weekly: Skim surface, check plants
• Monthly: Test water quality
• Seasonal: Plant care, prepare for winter
• Annual: Professional assessment

Annual Running Costs (After Conversion)

Common Conversion Challenges

Dechlorination

Chlorine must be completely eliminated before plants can thrive:

• Allow to dissipate naturally (2-4 weeks)
• May need partial water changes
• Test before planting
• Residual chloramines can persist

Algae Blooms

Common during establishment:

• System is finding balance
• Usually resolves in 4-8 weeks
• Avoid temptation to add chemicals
• Improve circulation if persistent

Plant Establishment

Plants need time to establish:

• May look sparse initially
• Growth accelerates after first season
• Some losses normal (10-20%)
• Replace as needed

Mindset Shift

Owners must adjust expectations:

• Water may not be chemically "sterile"
• Some organic matter is normal
• Occasional wildlife visitors
• Different kind of beauty

Case Study: Essex Pool Conversion

Original pool: 8m x 4m chlorinated pool (12 years old)

Issues: Liner needed replacing, heating costs high, maintenance tedious

Conversion scope:

• New regeneration zone (18m²) added to side
• Original pool retained as swim zone
• New biological filtration system
• Existing heating retained

Cost: £48,000

Timeline: 14 weeks to completion

Owner verdict: "We swim more than ever. No more red eyes, the garden is beautiful year-round, and we're saving over £1,500 a year in chemicals and running costs."

Getting Started with Conversion

Step 1: Initial Consultation

Contact us for a free assessment:

• Evaluate your existing pool
• Assess available space
• Discuss your goals
• Provide initial budget guidance

Step 2: Site Survey

Detailed evaluation including:

• Pool condition report
• Space measurement
• Soil assessment
• Design recommendations

Step 3: Design and Quote

Receive:

• Conversion design drawings
• Detailed specification
• Fixed-price quotation
• Timeline

Upload a photo of your existing pool and garden to start the conversation, or book a free consultation to discuss your conversion project directly with our team.