🌊 Calplas AFM/P-520 Side Mount Pool Filter – Up to 48,000 Litre Capacity

Superior semi-high bed filtration for crystal clear pool water, engineered for lasting performance.

💧 Product Overview

The Calplas AFM/P-520 is a premium semi-high bed pool filter engineered in Spain by one of the world’s most experienced filter manufacturers. Featuring a robust 520mm diameter tank constructed from hand-laid glass fibre reinforced polyester (GRP), this professional-grade filter delivers exceptional filtration performance for residential and small commercial swimming pools.

With a generous 900mm filter bed height and an impressive 0.20 m² filter area, the AFM/P-520 provides extended contact time between water and filter media, resulting in superior water clarity. The filter is specifically optimised for use with AFM® (Activated Filter Media) glass media, though it works equally well with traditional sand. Manufactured according to EN 13121-3 European standards, this filter combines industrial build quality with reliable everyday performance.

The steel-reinforced construction, transparent acrylic lid, and integrated sight glass make operation and maintenance straightforward, whilst the exclusive Besgo automatic backwash valve compatibility offers hands-free filter cleaning for ultimate convenience.

⭐ Key Features

• ✅ Semi-High Bed Design – 900mm filter bed height provides extended contact time for superior filtration performance
• ✅ GRP Construction – Hand-laid glass fibre reinforced polyester tank ensures absolute watertightness and corrosion resistance
• ✅ Steel Reinforcement – Additional steel reinforcement at high-stress points for exceptional durability
• ✅ AFM® Optimised Diffuser – Special diffuser prevents crater formation in filter bed for ideal water distribution
• ✅ Transparent Acrylic Lid – Clear top cover allows easy inspection of filter media and backwash monitoring
• ✅ Integrated Sight Glass – 2½” sight glass for clear backwash water monitoring
• ✅ Service Manhole – ø 215mm access point for straightforward media loading and maintenance
• ✅ Pressure Gauge Included – Factory-fitted gauge for accurate filter condition monitoring
• ✅ Drain Plug & Vent – Complete with all essential fittings for installation and winterisation
• ✅ Besgo Valve Compatible – Works with automatic or manual Besgo backwash valve systems (sold separately)
• ✅ EN 13121-3 Certified – Manufactured to European pressure vessel standards
• ✅ 5-Year Tank Warranty – Comprehensive manufacturer warranty for peace of mind

🔧 Technical Specifications

Specification	Value
Filter Type	Semi-High Bed Sand/AFM Filter
Tank Diameter	520 mm
Filter Area	0.20 m²
Filter Bed Height	900 mm
Flow Rate (Standard @ 30 m³/h/m²)	6 m³/h
Flow Rate (Backwash @ 50 m³/h/m²)	10 m³/h
Pool Capacity (6-hour turnover)	Up to 36,000 litres
Pool Capacity (8-hour turnover)	Up to 48,000 litres
Inlet/Outlet Connections	2″ Female Thread (F”)
Tank Height	1400 mm
Distance from Ground	405 mm
Connection Spacing	190 mm
Filter Opening at Top	ø 190 mm
Manhole Diameter	ø 215 mm
Sight Glass Size	2½”
Maximum Operating Pressure	2.5 bar
Test Pressure	3.75 bar
Maximum Temperature	40°C
Tank Material	GRP (Glass Fibre Reinforced Polyester)
Tank Colour	Blue RAL 5015 (White available on request)
Weight (Empty)	58 kg
Certification	EN 13121-3
Warranty	5 Years (Tank)

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📐 Pool Sizing Guide

The AFM/P-520 is designed for optimal performance with pools requiring a complete water turnover every 6-8 hours. With a standard flow rate of 6 m³/h, this filter delivers reliable filtration for small to medium residential pools.

Sizing Formula:

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

Pool Size Compatibility:

Pool Type	Volume Range	Suitability
🏠 Small above-ground	Up to 20,000 L	✅ Excellent – optimal turnover rates
🏠 Medium above-ground	20,000-36,000 L	✅ Ideal – 6-hour turnover achieved
🏠 Large above-ground	36,000-48,000 L	✅ Good – 8-hour turnover achieved
🏊 Small in-ground	Up to 36,000 L	✅ Ideal – maintains excellent clarity
🏊 Medium in-ground	36,000-48,000 L	✅ Suitable – 8-hour turnover
🏊 Large in-ground	50,000+ L	⚠️ Consider larger AFM/P model

This Filter:

📍 Standard Flow Rate: 6 m³/h
📍 Backwash Flow Rate: 10 m³/h  
📍 Optimal for pools up to: 36,000 litres (6-hour turnover)
📍 Maximum for pools up to: 48,000 litres (8-hour turnover)

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🔌 Installation Requirements

Plumbing Connections:

Requirement	Specification
Inlet Connection	2″ Female Thread (F”)
Outlet Connection	2″ Female Thread (F”)
Valve Position	Side Mount
Connection Spacing	190 mm centre-to-centre

Physical Installation:

Requirement	Details
Base	Solid, level concrete pad required
Total Height	1400 mm
Distance from Ground to Connections	405 mm
Clearance Above	Minimum 500 mm for lid removal and media access
Clearance Around	Minimum 600 mm for maintenance access

Pump Compatibility:

⚠️ Filter must be matched with an appropriate pump for optimal performance.
✅ Recommended pump flow rate: 4 - 6 m³/h (standard filtration)
✅ Backwash capable pump: Up to 10 m³/h
❌ Pump must not exceed filter's maximum flow rate of 10 m³/h

Valve Requirements:

The AFM/P-520 is designed for use with the Besgo automatic backwash valve system (available in automatic or manual versions). A coupling set is required and sold separately. The Besgo valve mounts directly to the filter or can be wall-mounted for flexible installation options.

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🧹 Maintenance Guide

Routine Maintenance Schedule:

Task	Frequency	Method
Check pressure gauge	Weekly	Normal operating range: 0.8-1.5 bar
Backwash filter	When pressure rises 0.5-1 bar above clean baseline	Run until sight glass shows clear water
Rinse after backwash	After each backwash	30-60 seconds to settle media
Inspect seals and gaskets	Seasonally	Replace if worn or cracked
Check media level	Annually	Top up if below recommended level
Full media replacement	Every 5-7 years (sand) or 10+ years (AFM®)	Replace completely

Pressure Gauge Guide:

📊 Clean filter baseline: 0.8 - 1.0 bar (typical)
📊 Backwash required: When pressure rises 0.5 - 1.0 bar above baseline
📊 Maximum operating pressure: 2.5 bar
⚠️ If pressure exceeds 2.5 bar, stop pump immediately and investigate

Winterisation (UK Climate):

For UK pool owners, proper winterisation is essential to prevent frost damage:

• Fully drain the filter tank using the drain plug
• Remove and safely store the drain plug
• Leave all valves in open position to allow any residual water to drain
• Cover the filter or store in a frost-free location if possible
• Never leave water standing in the filter during freezing conditions
• Inspect all seals before recommissioning in spring

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🪨 Filter Media Information

Media Capacity Requirements:

Media Type	Quantity Required
Sand/Gravel (25 kg bags)	5 bags Grade 1 + 5 bags Grade 2
AFM® Glass Media (21 kg bags)	6 bags AFM Grade 1 + 5 bags AFM Grade 2

Compatible Media Comparison:

Media Type	Filtration Rating	Lifespan	Key Benefits
Silica Sand	20-40 microns	5-7 years	Economical, widely available
AFM® Glass Media	Down to 1 micron*	10-15+ years	Superior clarity, self-sterilising, reduces chlorine demand
ZeoSand	3-5 microns	5 years	Enhanced clarity, ammonia reduction

*With proper flocculation

Why Choose AFM® Activated Filter Media:

AFM® (Activated Filter Media) is specifically optimised for this filter and offers significant advantages over traditional sand:

• Filters particles down to 1 micron (compared to 20-40 microns with sand)
• Self-sterilising surface prevents bacterial biofilm growth
• Reduces chlorine consumption by up to 50%
• Requires 50% less backwash water
• Maintains consistent performance for 10-15+ years
• Bio-resistant – eliminates trichloramine and chlorine smell
• NSF/ANSI certified for pools and drinking water

Signs Your Media Needs Replacing:

• Poor water clarity despite correct chemical balance
• Increasingly short filter cycles between backwashes
• Cloudy water returning to pool after filtration
• Media visible in pool (indicates lateral damage)
• Filter pressure consistently higher than normal even after backwash

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🔬 Filtration Performance

Performance Metric	Value
Filter Area	0.20 m²
Filter Bed Height	900 mm
Standard Flow Rate	6 m³/h @ 30 m³/h/m²
Backwash Flow Rate	10 m³/h @ 50 m³/h/m²

Micron Rating Guide:

Rating	What It Removes
40+ microns	Visible debris, leaves, large particles
20-40 microns	Sand, dirt, visible particles (typical sand filtration)
10-20 microns	Fine particles, some algae spores
5-10 microns	Very fine particles, most algae
1-5 microns	Ultra-fine particles, bacteria (achievable with AFM®)

The AFM/P-520’s semi-high bed design with 900mm media depth provides exceptional contact time, enhancing both mechanical filtration and flocculation processes for superior water clarity.

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⚙️ Besgo Valve Functions

The Calplas AFM/P-520 is designed for use with the Besgo automatic backwash valve system, offering simplified operation compared to traditional multiport valves:

Function	Description
Filter	Normal filtration mode – water flows through media bed
Backwash	Reverse flow cleans media – automated switching available
Rinse	Settles media after backwash (on applicable models)

Besgo Valve Advantages:

• ✅ Automatic backwash capability with timer control
• ✅ No need to stop pump during valve operation
• ✅ Fail-safe design returns to filter mode on power failure
• ✅ Operates in under 2 seconds
• ✅ Silent operation with no pressure hammer
• ✅ Low pressure loss for efficient backwashing
• ✅ Wall or filter-mounted installation options

💡 Note: The Besgo valve and coupling set are sold separately. Contact Parts4Tubs for compatible options.

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🎯 Ideal Applications

Application	Pool Size	Suitability
🏠 Residential above-ground pools	Up to 48,000 L	✅ Excellent choice
🏠 Residential in-ground pools	Up to 48,000 L	✅ Ideal for family pools
🏡 Garden pools and liner pools	Up to 36,000 L	✅ Perfect match
🧖 Hot tubs and swim spas	Up to 10,000 L	✅ Excellent with AFM® media
🏢 Small commercial installations	Up to 30,000 L	✅ With professional valve setup

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❓ Frequently Asked Questions

Q: What size pool will this filter handle? A: The AFM/P-520 is suitable for pools up to 48,000 litres with an 8-hour turnover time. For optimal 6-hour turnover, it’s ideal for pools up to 36,000 litres with its 6 m³/h flow rate.

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

Q: What filter media should I use? A: The filter is compatible with silica sand or AFM® glass media. For optimal performance, we recommend AFM® Activated Filter Media which provides filtration down to 1 micron and lasts 10+ years. Sand capacity is approximately 250 kg (5+5 bags of 25kg). AFM® capacity is 11 bags of 21 kg (6 bags Grade 1 + 5 bags Grade 2).

Q: How long does filter media last? A: Silica sand typically lasts 5-7 years before requiring replacement. AFM® glass media maintains performance for 10-15+ years and is self-sterilising, eliminating biofilm buildup.

Q: What pump do I need? A: Match with a pump delivering 4-6 m³/h for standard filtration. Ensure the pump can provide up to 10 m³/h for effective backwashing. Never exceed the filter’s maximum flow rate.

Q: Is a multiport valve included? A: No, the valve is sold separately. This filter is designed for use with the Besgo automatic backwash valve system (manual or automatic versions available). A coupling set is also required.

Q: What warranty is included? A: The Calplas AFM/P-520 comes with a 5-year tank warranty. Contact Parts4Tubs for full warranty terms and conditions.

Q: Can this filter be used with a heat pump or other equipment? A: Yes, the filter integrates into standard pool circulation systems and is compatible with heat pumps, salt chlorinators, and other water treatment equipment. Maximum operating temperature is 40°C.

Q: What colour options are available? A: The standard colour is blue (RAL 5015). White is available on request.

📥 Downloads & Resources

📄 Calplas AFM/P Series Technical Datasheet – Complete specifications for all AFM/P models

🏆 Why Choose the Calplas AFM/P-520

• ✅ Premium Spanish Engineering – Over 50 years of filter manufacturing expertise from Calplas
• ✅ Superior Build Quality – Hand-laid GRP construction with steel reinforcement for exceptional durability
• ✅ Outstanding Filtration – 900mm semi-high bed provides extended contact time for crystal clear water
• ✅ AFM® Optimised – Special diffuser designed specifically for activated glass media performance
• ✅ Easy Maintenance – Transparent lid and sight glass for simple monitoring and servicing
• ✅ Future-Proof Design – Compatible with Besgo automatic backwash for hands-free operation
• ✅ Proven Reliability – EN 13121-3 certified with 5-year tank warranty
• ✅ Excellent Value – Professional-grade filtration at a competitive price point

🤝 Why Buy from Parts4Tubs

• ✅ UK-based company with local customer support
• ✅ Fast UK delivery on all orders
• ✅ Expert advice from pool and spa specialists
• ✅ Competitive pricing on all Calplas products
• ✅ Full warranty support and after-sales service
• ✅ Easy returns within 30 days
• ✅ Compatible filter media, pumps, and spare parts available
• ✅ Besgo valves and coupling sets in stock

✨ Summary

The Calplas AFM/P-520 Side Mount Filter delivers professional-grade filtration performance for residential pools up to 48,000 litres. Featuring a robust 520mm GRP tank with 900mm semi-high bed design, this Spanish-engineered filter provides exceptional water clarity when paired with AFM® activated glass media. Complete with transparent inspection lid, integrated sight glass, and compatibility with Besgo automatic backwash systems, the AFM/P-520 combines industrial build quality with straightforward operation. Backed by a 5-year tank warranty and EN 13121-3 certification, this is the ideal choice for pool owners seeking reliable, low-maintenance filtration.

Order your Calplas AFM/P-520 today and enjoy crystal clear pool water all season long!