🌊 Calplas AFM-720 Semi-High Bed Sand Filter – 94,000 Litre Capacity

High-capacity filtration for large residential and light commercial pools demanding crystal clear water

📋 Product Overview

The Calplas AFM-720 represents the ideal choice for large residential and light commercial swimming pools up to 94,000 litres. With its substantial 720mm tank diameter and 0.40 m² filter area, this semi-high bed filter delivers impressive flow rates whilst maintaining the superior filtration depth that defines the AFM series.

Crafted by Calplas in Spain—a company with over 50 years of filter manufacturing expertise since 1970—the AFM-720 features hand-laminated glass-fibre reinforced polyester construction with internal steel reinforcement. The 900mm filter bed height combined with a specially designed AFM diffuser ensures optimal water distribution and exceptional particle removal efficiency.

This filter bridges the gap between residential and commercial applications, offering the robust performance needed for busy family pools, holiday rental properties, and small commercial installations. The generous 305mm service manhole and 3″ sight glass simplify maintenance, whilst Besgo valve compatibility enables full automation of backwash cycles.

With a standard flow rate of 11.7 m³/h and backwash capacity of 19.5 m³/h, the AFM-720 provides the throughput required for larger water volumes without compromising on filtration quality.

🌟 Key Features

✅ 720mm Tank Diameter – Substantial 0.40 m² filter area handles high flow demands with ease

✅ Semi-High Bed Design – 900mm filter bed height delivers extended water contact time for thorough filtration

✅ High Flow Capacity – 11.7 m³/h standard flow rate suits pools up to 94,000 litres

✅ AFM-Optimised Diffuser – Prevents channelling and crater formation for consistent filtration performance

✅ Heavy-Duty GRP Construction – Hand-laminated glass-fibre reinforced polyester with steel reinforcement

✅ Large Service Manhole – ø305mm access with transparent acrylic cover for straightforward media management

✅ 3″ Sight Glass – Clear visual monitoring of backwash effectiveness

✅ Besgo Valve Compatible – Supports both automatic and manual backwash valve configurations

✅ Complete Accessory Package – Pressure gauge, drain plug, and air vent included as standard

✅ Versatile Media Options – Optimised for AFM activated glass media, also compatible with silica sand

✅ 5-Year Tank Warranty – Manufacturer confidence backed by comprehensive warranty coverage

✅ EN 13121-3 Certified – European pressure vessel standards compliance

📊 Technical Specifications

Specification	Value
Filter Type	Semi-high bed sand/AFM filter
Tank Diameter	720 mm
Filter Area	0.40 m²
Filter Bed Height	900 mm
Overall Height	1440 mm
Distance from Ground (A)	420 mm
Connection Spacing (B)	190 mm
Inlet/Outlet Connections	2″ Female thread (GAS)
Filter Opening (Top)	ø190 mm
Service Manhole	ø305 mm
Sight Glass	3″
Working Pressure	2.5 bar
Test Pressure	3.75 bar
Maximum Temperature	40°C
Tank Material	Hand-laminated GRP with steel reinforcement
Tank Colour	Blue RAL 5015 (white available on request)
Weight (Empty)	88 kg
Flow Rate @ 30 m³/h/m²	11.7 m³/h
Backwash Flow Rate @ 50 m³/h/m²	19.5 m³/h
AFM Media Capacity	22 bags (11× Grade 1 + 11× Grade 2, 21kg bags)
Sand Media Capacity	20 bags (10× fine + 10× coarse, 25kg bags)
Warranty	5 years (tank)

⚠️ Note: Higher working pressure versions (up to 7 bar) available on request from manufacturer.

📐 Pool Sizing Guide

Sizing Principle: The filter flow rate should turn over the entire pool volume within 6-8 hours for optimal water quality.

Formula:

Required Flow Rate (m³/h) = Pool Volume (m³) ÷ Turnover Time (hours)

This Filter:

📍 Standard Flow Rate: 11.7 m³/h (at 30 m³/h/m²)
📍 Backwash Flow Rate: 19.5 m³/h (at 50 m³/h/m²)

Pool Size Compatibility:

Pool Type	Volume Range	Suitability
🏠 Large above-ground	50,000-75,000 L	✅ Excellent capacity
🏠 Extra-large above-ground	75,000-94,000 L	✅ Well suited
🏊 Medium in-ground	50,000-70,000 L	✅ Optimal turnover
🏊 Large in-ground	70,000-94,000 L	✅ Ideal match
🏨 Holiday rental pools	Up to 70,000 L	✅ Robust for higher bather loads
🏢 Small commercial	Up to 80,000 L	✅ Suitable for light commercial use
🏊 Very large pools	94,000+ L	⚠️ Consider AFM-840 or AFM-960

Turnover Calculations:

Pool Volume	Turnover Time	Suitability
70,000 L (70 m³)	6 hours	✅ Optimal
82,000 L (82 m³)	7 hours	✅ Good
94,000 L (94 m³)	8 hours	✅ Acceptable maximum

🔌 Installation Requirements

Plumbing:

Requirement	Specification
Inlet Connection	2″ Female thread (GAS)
Outlet Connection	2″ Female thread (GAS)
Valve Position	Side-mounted (Besgo compatible)
Connection Spacing	190 mm between inlet/outlet

Physical Installation:

Requirement	Details
Base	Solid, level concrete pad capable of supporting 550+ kg when filled
Filter Height	1440 mm total
Ground Clearance	420 mm from floor to connections
Clearance Above	Minimum 600 mm for lid removal and media access
Clearance Around	Minimum 450 mm for valve operation and maintenance

Pump Compatibility:

⚠️ Filter must be matched with appropriate pump.
✅ Recommended pump flow rate: 9-11.7 m³/h for filtration
✅ Backwash pump capacity: 15-19.5 m³/h for effective backwashing
❌ Pump must not exceed filter's maximum flow rate of 19.5 m³/h

Valve Options: The Calplas AFM-720 is designed for use with Besgo backwash valves (wall-mounted, coupling set required separately). Choose from:

• Manual Besgo valve for budget-conscious installations
• Automatic Besgo valve with solenoid control for hands-free operation
• Control panel available for scheduled automatic backwashing

🧹 Maintenance Guide

Routine Maintenance:

Task	When	How
Check pressure gauge	Weekly	Normal operating: 0.5-1.0 bar
Backwash filter	When pressure rises 0.5 bar above baseline	Run until sight glass shows clear water
Rinse after backwash	After each backwash	30-60 seconds to settle media
Inspect transparent lid	Monthly	Check for debris, cracks, seal condition
Check sight glass clarity	During backwash	Water should run clear within 2-4 minutes
Inspect media level	Annually	Top up if level has dropped
Full media replacement	Sand: 5-7 years / AFM: 10-15 years	Replace completely

Pressure Gauge Guide:

📊 Clean filter baseline: 0.5-0.8 bar
📊 Backwash needed: When 0.5 bar above baseline
📊 Maximum safe operating: 2.5 bar
⚠️ If pressure exceeds 2.5 bar, stop pump immediately and investigate

Backwash Procedure:

1. Turn off pool pump (unless using Besgo automatic valve)
2. Set valve to backwash position
3. Turn on pump and run until sight glass shows clear water (typically 3-5 minutes for larger filters)
4. Turn off pump
5. Set valve to rinse position
6. Run pump for 30-60 seconds to settle media
7. Return valve to filter position
8. Resume normal filtration

Winterisation (UK Climate):

• Drain filter tank completely via drain plug
• Remove and safely store drain plug
• Leave tank lid slightly open to prevent pressure build-up
• Cover filter or relocate to frost-free location if possible
• Never leave water in filter during freezing conditions – ice expansion can crack the tank
• Disconnect and drain all associated pipework

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🪨 Filter Media Information

The Calplas AFM-720 is specifically designed for optimal performance with AFM (Activated Filter Media) but also performs excellently with traditional silica sand.

Compatible Media:

Media Type	Filtration Rating	Lifespan	Benefits
AFM (Activated Filter Media)	4-5 microns (without flocculant)	10-15+ years	Superior clarity, self-sterilising, bio-resistant
AFM with APF/ZPM	Down to 1 micron	10-15+ years	Exceptional clarity, removes bacteria
Silica Sand	20-40 microns	5-7 years	Economical, widely available
Glass Sand	10-15 microns	8-10 years	Better than sand, good value

AFM Media Requirements for AFM-720:

Grade	Bag Size	Quantity	Total Weight
AFM Grade 1 (0.4-1.0mm)	21 kg	11 bags	231 kg
AFM Grade 2 (0.7-2.0mm)	21 kg	11 bags	231 kg
Total AFM		22 bags	462 kg

Sand Media Requirements for AFM-720:

Grade	Bag Size	Quantity	Total Weight
Fine Sand (0.4-0.8mm)	25 kg	10 bags	250 kg
Coarse Sand/Gravel (0.7-1.2mm)	25 kg	10 bags	250 kg
Total Sand		20 bags	500 kg

💡 Tip: When filling, always add the coarser grade first (Grade 2 AFM or coarse sand/gravel), then add the finer grade on top. For this filter size, consider having assistance due to the substantial media weight.

Signs Media Needs Replacing:

• Poor water clarity despite correct chemical balance
• Very short filter cycles between backwashes
• Cloudy water returning to pool during filtration
• Media visible in pool (indicates damaged laterals)
• Excessive media loss during backwash

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🔬 Filtration Performance

Metric	Value
Filter Area	0.40 m²
Filter Bed Height	900 mm
Standard Flow Rate	11.7 m³/h
Filtration Rating (AFM)	4-5 microns nominal
Filtration Rating (Sand)	20-40 microns

Why AFM Outperforms Sand:

AFM (Activated Filter Media) is manufactured from specially processed recycled glass with a unique activation process that creates a negatively-charged, self-sterilising surface. This provides:

• 40× greater surface area than sand for superior particle capture
• Bio-resistant properties preventing bacterial colonisation
• Self-sterilising surface that doesn’t support biofilm growth
• Consistent performance without the degradation seen in sand filters after 6-12 months
• Reduced chemical consumption due to cleaner water and no bacterial growth

Micron Rating Guide:

Rating	What It Catches
40+ microns	Visible debris, leaves, large particles
20-40 microns	Sand, dirt, visible particles (typical sand filter)
10-20 microns	Fine particles, some algae spores
4-5 microns	Very fine particles, most algae (AFM without flocculant)
1 micron	Bacteria, ultra-fine particles (AFM with APF/ZPM)

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⚙️ Besgo Valve System

The Calplas AFM-720 is designed for use with the Swiss-engineered Besgo backwash valve system, which replaces traditional 6-way multiport valves with a more efficient, automated solution.

Besgo Valve Positions:

Position	Function
Filter	Normal filtration mode – water flows through media to pool
Backwash	Reversed flow cleans media, water to waste

Besgo System Advantages:

• ✅ Automatic switching between filter and backwash modes
• ✅ No need to turn pump off during valve changeover
• ✅ Fail-safe design – returns to filter mode on power failure
• ✅ Lower pressure loss than traditional multiport valves
• ✅ Silent operation with no pressure hammer
• ✅ Valve operates in less than 2 seconds
• ✅ Wall-mounted design saves floor space
• ✅ Control panel available for scheduled automatic backwashing

⚠️ Note: Besgo valve and coupling set sold separately. 3-5 bar mains water pressure or compressed air required for valve actuation.

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🎯 Ideal Applications

Application	Pool Size	Suitability
🏠 Large residential in-ground	Up to 94,000 L	✅ Ideal
🏠 Extra-large above-ground	Up to 94,000 L	✅ Excellent
🏨 Holiday let / rental properties	Up to 70,000 L	✅ Robust for variable use
🏢 Small commercial pools	Up to 80,000 L	✅ Well suited
🧖 Commercial swim spas	Up to 40,000 L	✅ Generous capacity
🏨 Hotel pools (light use)	Up to 70,000 L	✅ Good for moderate bather loads

Best Suited For:

• Large residential pools requiring high-volume filtration
• Properties with higher bather loads or frequent use
• Holiday rental pools needing reliable, low-maintenance operation
• Light commercial applications with moderate usage
• Pool owners seeking the balance of capacity and manageable size

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❓ Frequently Asked Questions

Q: What size pool will this filter handle? A: The Calplas AFM-720 is suitable for pools up to 94,000 litres with a flow rate of 11.7 m³/h, providing an 8-hour turnover. For optimal 6-hour turnover, it’s ideal for pools up to 70,000 litres.

Q: How often do I need to backwash? A: Backwash when the pressure gauge reads 0.5 bar above your clean baseline reading. This is typically every 1-2 weeks depending on pool usage and debris load.

Q: What filter media should I use? A: The filter is optimised for AFM (Activated Filter Media) with a capacity of 22 bags (462 kg total). Traditional silica sand can also be used – 20 bags (500 kg total).

Q: How long does filter media last? A: AFM media lasts 10-15+ years without replacement. Traditional sand should be replaced every 5-7 years.

Q: What pump do I need? A: Match with a pump delivering 9-11.7 m³/h for normal filtration. Ensure the pump can deliver 15-19.5 m³/h for effective backwashing. Do not exceed 19.5 m³/h maximum.

Q: How does the AFM-720 compare to smaller models? A: The AFM-720 offers 33% more filter area than the AFM-640 (0.40 m² vs 0.30 m²) and 100% more than the AFM-520. It handles pools up to 94,000L compared to 74,000L (AFM-640) and 48,000L (AFM-520).

Q: Is this filter suitable for commercial use? A: Yes, the AFM-720 is suitable for light commercial applications including small hotel pools, holiday lets, and swim schools with moderate bather loads. For busier commercial pools, consider the AFM-840 or AFM-960.

Q: What warranty is included? A: Calplas provides a 5-year warranty on the filter tank. Contact Parts4Tubs for full warranty terms and conditions.

Q: How heavy is the filter when filled with media? A: Empty weight is 88 kg. With AFM media (462 kg) plus water, expect a total operating weight of approximately 550-600 kg. Ensure your installation base can support this load.

Q: Can I use this filter with an existing pump? A: Yes, provided your pump delivers between 9-19.5 m³/h. The 2″ connections are standard and compatible with most pool plumbing systems.

📥 Downloads & Resources

📄 Technical Datasheet (PDF) – Complete specifications for AFM series

🏆 Why Choose the Calplas AFM-720

✅ High-Volume Capacity – 0.40 m² filter area handles pools up to 94,000 litres

✅ Versatile Application – Bridges residential and light commercial requirements

✅ Premium Construction – Hand-laminated GRP with steel reinforcement built to last

✅ Superior Filtration Depth – 900mm bed height for exceptional water contact time

✅ Easy Maintenance – Large 305mm manhole and 3″ sight glass simplify servicing

✅ Automation Ready – Full Besgo valve system compatibility

✅ Proven Manufacturer – Calplas expertise since 1970

✅ 5-Year Warranty – Comprehensive tank warranty coverage

🛒 Why Buy from Parts4Tubs

✅ UK-based company with knowledgeable local support

✅ Fast UK delivery on in-stock items

✅ Expert advice from pool and spa specialists

✅ Competitive pricing on premium filtration equipment

✅ Full warranty support – we handle warranty claims directly

✅ Easy returns within 30 days if not completely satisfied

✅ Compatible accessories available – AFM media, Besgo valves, spare parts

✅ Technical guidance for sizing and installation queries

💧 Summary

The Calplas AFM-720 delivers high-capacity filtration for large residential pools and light commercial applications up to 94,000 litres. Featuring a 720mm diameter tank with 0.40 m² filter area and 11.7 m³/h flow rate, this Spanish-manufactured filter provides the performance needed for demanding installations whilst maintaining the premium build quality and AFM-optimised design of the Calplas range. The 900mm filter bed depth, 305mm service manhole, and Besgo valve compatibility ensure outstanding water clarity with convenient maintenance. Backed by a 5-year tank warranty and compatible with long-lasting AFM media, the AFM-720 represents an excellent investment for pool owners requiring reliable, high-volume filtration.