🏊 Calplas AFM-960 Semi-High Bed Sand Filter – 168,000 Litre Capacity

The flagship of the AFM range: maximum filtration power for large commercial and luxury residential pools

💧 Product Overview

The Calplas AFM-960 stands as the flagship of the AFM filter range, delivering exceptional filtration capacity for large commercial pools and prestigious residential installations up to 168,000 litres. With its commanding 960mm tank diameter and impressive 0.70 m² filter area, this semi-high bed filter represents the pinnacle of Calplas engineering.

Built by Calplas in Spain—filter manufacturing specialists since 1970—the AFM-960 features robust hand-laminated glass-fibre reinforced polyester construction with comprehensive internal steel reinforcement. The 900mm filter bed depth combined with the specially designed AFM diffuser ensures outstanding particle removal even at the substantial 21 m³/h flow rate.

This filter is purpose-built for demanding applications: hotel pools, leisure centres, swim schools, hydrotherapy facilities, and large luxury residential pools where water quality and reliability are non-negotiable. The upgraded 2½” connections and powerful 35 m³/h backwash capacity ensure efficient water handling at commercial scale.

With its generous 355mm service manhole—the largest in the range—plus 3″ sight glass and full Besgo automatic valve compatibility, the AFM-960 combines maximum performance with practical serviceability for professional pool operators.

⭐ Key Features

✅ 960mm Tank Diameter – Impressive 0.70 m² filter area for maximum throughput

✅ Highest Flow Capacity – 21 m³/h standard rate handles pools up to 168,000 litres

✅ Powerful Backwash – 35 m³/h ensures thorough media cleaning at commercial scale

✅ Upgraded 2½” Connections – Larger pipework for reduced pressure loss at high flow

✅ Semi-High Bed Design – 900mm filter bed height for superior water contact time

✅ AFM-Optimised Diffuser – Engineered for even distribution across the large filter area

✅ Heavy-Duty Construction – Hand-laminated GRP with extensive steel reinforcement

✅ Largest Service Manhole – ø355mm access for easy media management

✅ 3″ Sight Glass – Clear monitoring of backwash effectiveness

✅ Besgo Valve Compatible – Full support for automated backwash systems

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

✅ Three-Grade Media Configuration – Optimised for maximum filtration efficiency

✅ 5-Year Tank Warranty – Comprehensive manufacturer-backed coverage

📊 Technical Specifications

Specification	Value
Filter Type	Semi-high bed sand/AFM filter
Tank Diameter	960 mm
Filter Area	0.70 m²
Filter Bed Height	900 mm
Overall Height	1520 mm
Distance from Ground (A)	405 mm
Connection Spacing (B)	250 mm
Inlet/Outlet Connections	2½” Female thread (GAS)
Filter Opening (Top)	ø205 mm
Service Manhole	ø355 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)	125 kg
Flow Rate @ 30 m³/h/m²	21 m³/h
Backwash Flow Rate @ 50 m³/h/m²	35 m³/h
AFM Media Capacity	44 bags (22× Grade 1 + 11× Grade 2 + 11× Grade 3, 21kg bags)
Sand Media Capacity	41 bags (21× fine + 10× medium + 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: 21 m³/h (at 30 m³/h/m²)
📍 Backwash Flow Rate: 35 m³/h (at 50 m³/h/m²)

Pool Size Compatibility:

Pool Type	Volume Range	Suitability
🏠 Luxury residential	100,000-168,000 L	✅ Ideal for large private pools
🏊 Very large in-ground	100,000-126,000 L	✅ Optimal 6-hour turnover
🏊 Extra-large pools	126,000-168,000 L	✅ Well suited
🏨 Hotel pools	Up to 150,000 L	✅ Excellent for commercial use
🏢 Leisure centres	Up to 126,000 L	✅ Robust capacity
🏢 Swim schools	Up to 100,000 L	✅ Handles high bather loads
🏢 Public pools	Up to 126,000 L	✅ Good for moderate-heavy use
🏊 Pools over 168,000 L	168,000+ L	⚠️ Consider multiple filters

Turnover Calculations:

Pool Volume	Turnover Time	Suitability
126,000 L (126 m³)	6 hours	✅ Optimal
147,000 L (147 m³)	7 hours	✅ Good
168,000 L (168 m³)	8 hours	✅ Acceptable maximum

🔌 Installation Requirements

Plumbing:

Requirement	Specification
Inlet Connection	2½” Female thread (GAS)
Outlet Connection	2½” Female thread (GAS)
Valve Position	Side-mounted (Besgo compatible)
Connection Spacing	250 mm between inlet/outlet

⚠️ Important: The AFM-960 features 2½” connections (larger than the 2″ on smaller models). Ensure pipework and valves are sized accordingly.

Physical Installation:

Requirement	Details
Base	Reinforced concrete pad capable of supporting 1,100+ kg when filled
Filter Height	1520 mm total
Ground Clearance	405 mm from floor to connections
Clearance Above	Minimum 700 mm for lid removal and media access
Clearance Around	Minimum 600 mm for valve operation and maintenance

Pump Compatibility:

⚠️ Filter must be matched with appropriate commercial-grade pump.
✅ Recommended pump flow rate: 16-21 m³/h for filtration
✅ Backwash pump capacity: 28-35 m³/h for effective backwashing
❌ Pump must not exceed filter's maximum flow rate of 35 m³/h

Valve Options: The Calplas AFM-960 is designed for use with Besgo backwash valves (wall-mounted, coupling set required separately). For this filter size:

• Automatic Besgo valve with solenoid control recommended for commercial applications
• Control panel strongly advised for scheduled automatic backwash management
• Manual override capability for maintenance situations

---

🔄 Maintenance Guide

Routine Maintenance:

Task	When	How
Check pressure gauge	Daily (commercial) / Weekly (residential)	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	45-60 seconds to settle media
Inspect transparent lid	Weekly (commercial) / Monthly (residential)	Check for debris, cracks, seal condition
Check sight glass clarity	During backwash	Water should run clear within 4-6 minutes
Inspect media level	Bi-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 5-7 minutes for this filter size)
4. Turn off pump
5. Set valve to rinse position
6. Run pump for 45-60 seconds to settle media
7. Return valve to filter position
8. Resume normal filtration

Commercial Backwash Scheduling: For commercial pools with high bather loads, consider:

• Daily backwash during peak season
• Pressure-triggered automatic backwash via Besgo control panel
• Logging of backwash frequency and duration for compliance records

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 ensure plant room is frost-protected
• Never leave water in filter during freezing conditions – ice expansion can crack the tank
• Disconnect and drain all associated pipework
• For commercial installations, maintain frost protection heating if required

---

🪨 Filter Media Information

The Calplas AFM-960 utilises a three-layer media configuration for optimal filtration performance and backwash efficiency at commercial scale.

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-960:

Grade	Bag Size	Quantity	Total Weight	Layer Position
AFM Grade 3 (2.0-4.0mm)	21 kg	11 bags	231 kg	Bottom (support)
AFM Grade 2 (0.7-2.0mm)	21 kg	11 bags	231 kg	Middle
AFM Grade 1 (0.4-1.0mm)	21 kg	22 bags	462 kg	Top (filtration)
Total AFM		44 bags	924 kg

Sand Media Requirements for AFM-960:

Grade	Bag Size	Quantity	Total Weight	Layer Position
Coarse Gravel (2-4mm)	25 kg	10 bags	250 kg	Bottom (support)
Medium Sand (0.7-1.2mm)	25 kg	10 bags	250 kg	Middle
Fine Sand (0.4-0.8mm)	25 kg	21 bags	525 kg	Top (filtration)
Total Sand		41 bags	1,025 kg

💡 Professional Installation Required: Due to the substantial media weight (924 kg AFM / 1,025 kg sand), professional installation is essential. Media should be delivered by pallet and mechanical handling equipment may be required.

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

---

🔬 Filtration Performance

Metric	Value
Filter Area	0.70 m²
Filter Bed Height	900 mm
Standard Flow Rate	21 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

Three-Layer Configuration Benefits:

The AFM-960’s three-grade media configuration provides:

• Optimal flow distribution through graduated particle sizes
• Enhanced backwash efficiency with proper support layers
• Extended filter runs between backwashes
• Superior particle capture across size ranges
• Reduced media migration during high-flow operation

---

⚙️ Besgo Valve System

The Calplas AFM-960 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: For the AFM-960, ensure Besgo valve is correctly sized for 2½” pipework. Valve and coupling set sold separately. 3-5 bar mains water pressure or compressed air required for valve actuation.

🎯 Ideal Applications

Application	Pool Size	Suitability
🏠 Large luxury residential	Up to 168,000 L	✅ Premium choice
🏨 Hotel pools	Up to 150,000 L	✅ Excellent
🏨 Resort pools	Up to 126,000 L	✅ Ideal for high bather loads
🏢 Leisure centres	Up to 126,000 L	✅ Commercial-grade performance
🏢 Swim schools	Up to 100,000 L	✅ Handles intensive use
🏢 Hydrotherapy facilities	Up to 80,000 L	✅ Generous capacity
🏢 Health clubs	Up to 126,000 L	✅ Well suited
🏢 Public pools	Up to 126,000 L	✅ Good for moderate-heavy use
🏢 Competition pools	Up to 168,000 L	✅ Suitable with proper sizing

Best Suited For:

• Large commercial pools requiring maximum filtration capacity
• Luxury residential installations demanding the best
• Facilities with high bather loads and strict water quality requirements
• Applications where reliability and longevity are paramount
• Professional installations requiring automated operation

❓ Frequently Asked Questions

Q: What size pool will this filter handle? A: The Calplas AFM-960 is suitable for pools up to 168,000 litres with a flow rate of 21 m³/h, providing an 8-hour turnover. For optimal 6-hour turnover, it’s ideal for pools up to 126,000 litres.

Q: How often do I need to backwash? A: For commercial pools, daily backwashing is common during peak season. For residential use, backwash when the pressure gauge reads 0.5 bar above baseline. Automatic pressure-triggered backwashing via Besgo control panel is recommended.

Q: What filter media should I use? A: The filter uses a three-layer configuration. AFM capacity is 44 bags (924 kg total). Traditional sand can also be used – 41 bags (1,025 kg total).

Q: Why are the connections 2½” instead of 2″? A: The AFM-960’s high flow rate (21 m³/h filtration, 35 m³/h backwash) requires larger pipework to minimise pressure loss and ensure efficient water handling. Ensure your installation uses appropriately sized pipes and valves.

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. The extended lifespan of AFM makes it particularly cost-effective for commercial installations.

Q: What pump do I need? A: Match with a commercial-grade pump delivering 16-21 m³/h for normal filtration. Ensure the pump can deliver 28-35 m³/h for effective backwashing. Do not exceed 35 m³/h maximum.

Q: How does the AFM-960 compare to smaller models? A: The AFM-960 is the largest in the range with 0.70 m² filter area (vs 0.52 m² for AFM-840), 35% higher flow rate (21 m³/h vs 15.6 m³/h), and larger 2½” connections. It handles pools up to 168,000L compared to 125,000L for AFM-840.

Q: Is this filter suitable for public pools? A: Yes, the AFM-960 is designed for commercial applications including public pools, leisure centres, and hotel facilities. For very large or heavily-used public pools, multiple filters may be required.

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? A: Empty weight is 125 kg. With AFM media (924 kg) plus water, expect a total operating weight of approximately 1,100-1,200 kg. Professional installation with appropriate lifting equipment and a reinforced concrete base are essential.

Q: Can I install this filter myself? A: Due to the size, weight, and commercial nature of this filter, professional installation is strongly recommended. The media alone weighs nearly a tonne, requiring mechanical handling equipment for safe installation.

📄 Downloads & Resources

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

🏆 Why Choose the Calplas AFM-960

✅ Maximum Capacity – 0.70 m² filter area handles pools up to 168,000 litres

✅ Commercial-Grade Performance – 21 m³/h flow rate with 35 m³/h backwash capability

✅ Upgraded Connections – 2½” inlet/outlet for optimal high-flow performance

✅ Largest Service Access – 355mm manhole simplifies commercial maintenance

✅ Three-Layer Media Design – Optimised filtration and backwash efficiency

✅ Premium Construction – Heavy-duty GRP with comprehensive steel reinforcement

✅ Proven Reliability – Calplas manufacturing excellence since 1970

✅ 5-Year Warranty – Comprehensive manufacturer-backed 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

✅ Commercial project support – technical guidance for professional installations

✨ Summary

The Calplas AFM-960 represents the ultimate in the AFM filter range, delivering maximum filtration capacity for large commercial pools and luxury residential installations up to 168,000 litres. With its 960mm diameter tank, 0.70 m² filter area, and powerful 21 m³/h flow rate through upgraded 2½” connections, this Spanish-manufactured flagship filter provides the performance demanded by hotels, leisure centres, and discerning private pool owners. The three-layer media configuration optimises both filtration efficiency and backwash effectiveness, whilst the 355mm service manhole—the largest in the range—ensures practical serviceability. Backed by a 5-year tank warranty and designed for 10-15+ year AFM media lifespan, the AFM-960 represents the professional choice for installations where water quality excellence is the only option.