🏊 Calplas HFS-35 960mm Side Mount Sand Filter – Up to 168,000 Litre Pool Capacity
Advanced filtration for the ultimate swimming experience in large pools
🌊 Product Overview
The Calplas HFS-35 is the flagship model in the HFS range, delivering industrial-strength filtration for the largest residential pools and demanding commercial applications. Featuring an impressive 960mm diameter tank constructed from hand-laid glass reinforced polyester (GRP) with internal steel reinforcement, this Spanish-manufactured filter represents the pinnacle of Calplas engineering excellence.
The HFS series is distinguished by its significantly taller design, providing almost 50% more filter medium than comparable standard filters. This extended filter bed maximises water contact time, resulting in exceptional filtration efficiency and superior flocculation for consistently crystal-clear pool water even under the most demanding conditions.
As the largest model in the HFS-15 and above range, the HFS-35 features an extra-large 355mm transparent filter cover, upgraded 2½” connections for maximum flow capacity, and contains approximately 20% more filter medium than smaller models. The integrated special AFM diffusor ensures optimal water distribution across the entire filter bed, eliminating channelling and crater formation. Capable of handling pools up to 168,000 litres with an 8-hour turnover, the HFS-35 is the definitive choice for large estate pools, commercial leisure facilities, and installations where uncompromising water quality is essential.
⭐ Key Features
✅ Premium GRP Construction – Hand-laid glass reinforced polyester tank with internal steel reinforcement, manufactured to EN 13121-3 standards for maximum strength
✅ 50% Greater Media Capacity – Tallest filter bed in the range provides almost 50% more filter medium for unrivalled filtration performance
✅ Extra-Large 355mm Transparent Lid – Oversized inspection port allows comprehensive visual monitoring of media condition
✅ Upgraded 2½” Connections – Larger inlet/outlet ports handle higher flow rates with reduced pressure loss
✅ Integrated AFM Diffusor – Specialised water distribution system ensures uniform flow across the entire 0.70 m² filter area
✅ 2.5 Bar Industrial Pressure Rating – Heavy-duty pressure handling with 3.75 bar test pressure (7 bar versions available on request)
✅ 6-Way Valve Compatible – Accepts exclusive Calplas 6-way multiport valve with automatic or manual operation; Besgo backwash valve fits as standard
✅ Three-Grade Media Configuration – Optimised for traditional sand/gravel or advanced AFM activated filter media achieving filtration down to 1 micron
✅ 40°C Temperature Tolerance – Suitable for heated pools, warm climates, and high-intensity commercial use
✅ Complete Filter Package – Supplied with pressure gauge, air vent, drain plug, and extra-large transparent lid as standard
✅ 5-Year Tank Warranty – Comprehensive manufacturer warranty on the flagship model
✅ White Option Available – Alternative colour to suit premium installation aesthetics
📊 Technical Specifications
| Specification | Value |
|---|---|
| Filter Type | Sand / AFM Media Filter |
| Tank Diameter | 960 mm |
| Overall Height | 1,240 mm |
| Filter Area | 0.70 m² |
| Flow Rate (Normal Filtration) | 21 m³/h (at 30 m³/h/m²) |
| Flow Rate (Backwash Capacity) | 35 m³/h (at 50 m³/h/m²) |
| Pool Capacity (6-hr Turnover) | Up to 126,000 litres |
| Pool Capacity (8-hr Turnover) | Up to 168,000 litres |
| Sand Capacity | 28 kg sand + 6 kg gravel |
| AFM Media Capacity | 15 × 21 kg Grade 1 + 8 × 21 kg Grade 2 + 7 × 21 kg Grade 3 |
| Maximum Operating Pressure | 2.5 bar |
| Test Pressure | 3.75 bar |
| Temperature Rating | Up to 40°C |
| Inlet/Outlet Connections | 2½” (63 mm) threaded |
| Filter Opening Diameter | 355 mm |
| Distance from Ground | 360 mm |
| Distance Between Connections | 250 mm |
| Tank Material | Hand-laid GRP (Glass Reinforced Polyester) |
| Reinforcement | Internal steel reinforced |
| Weight (Empty) | 75 kg |
| Valve Type | Side mount (6-way valve optional) |
| Warranty | 5 years (tank) |
| Product Code | 1519250135 |
| Manufacturer | Calplas (Spain) |
| Manufacturing Standard | EN 13121-3 |
📏 Pool Sizing Guide
Sizing Principle: The filter flow rate should achieve complete pool water turnover within 6-8 hours for optimal clarity, hygiene, and chemical efficiency.
Formula:
Required Flow Rate (m³/h) = Pool Volume (m³) ÷ Turnover Time (hours)
Pool Size Compatibility:
| Pool Type | Volume Range | Suitability |
|---|---|---|
| 🏠 Large in-ground residential | 80,000 – 120,000 L | ✅ Excellent – generous capacity |
| 🏠 Extra-large estate pools | 120,000 – 168,000 L | ✅ Excellent – optimal match |
| 🏢 Commercial leisure pools | Up to 126,000 L | ✅ Excellent – 6-hr turnover |
| 🏨 Hotel/resort pools | Up to 126,000 L | ✅ Excellent – handles high traffic |
| 🏫 School/institutional pools | Up to 126,000 L | ✅ Good – robust performance |
| 🏊 Competition/training pools | Up to 140,000 L | ✅ Good – professional grade |
This Filter:
📍 Normal Filtration Flow Rate: 21 m³/h
📍 Maximum Backwash Flow Rate: 35 m³/h
📍 Recommended Pool Size: Up to 126,000 litres (6-hour turnover)
📍 Maximum Pool Size: Up to 168,000 litres (8-hour turnover)
🔌 Installation Requirements
Plumbing:
| Requirement | Specification |
|---|---|
| Inlet Connection | 2½” (63 mm) female thread |
| Outlet Connection | 2½” (63 mm) female thread |
| Connection Spacing | 250 mm between ports |
| Valve Position | Side mount |
⚠️ Note: The HFS-35 uses larger 2½” connections compared to 2″ on smaller HFS models. Ensure compatible pipework and valve selection.
Physical Installation:
| Requirement | Details |
|---|---|
| Base | Reinforced concrete pad capable of supporting 600+ kg when filled |
| Minimum Height Clearance | 950 mm above filter for lid removal |
| Distance from Ground | 360 mm (integrated legs) |
| Access Clearance | 800 mm all around for servicing |
| Weight Consideration | 75 kg empty; plan for delivery and positioning |
Pump Compatibility:
⚠️ Critical: Filter must be paired with an appropriately rated pump for optimal performance.
| Parameter | Specification |
|---|---|
| Recommended Pump Flow Rate | 14 – 22 m³/h |
| Maximum Pump Flow Rate | Do not exceed 35 m³/h |
| Pump Connection | 2½” or adapt from 2″ with appropriate fittings |
| Pump Head | Factor in filter pressure drop when sizing |
💡 Tip: For finest filtration results, operate towards the lower end of the recommended flow range. Higher flow rates reduce media contact time and filtration quality.
🔄 Maintenance Guide
Routine Maintenance:
| Task | Frequency | Procedure |
|---|---|---|
| Check pressure gauge | Weekly | Record baseline; monitor for pressure increases |
| Backwash filter | When pressure rises 0.5-1 bar | Run until sight glass clears (4-5 minutes for this size) |
| Rinse after backwash | After every backwash | Run 60-90 seconds to fully resettle media |
| Inspect transparent lid | Monthly | Check for cracks, seal condition, clarity |
| Check O-rings and seals | Seasonally | Replace if worn, hardened, or showing leakage |
| Inspect media level | Annually | Top up if significantly settled |
| Full media replacement | 5-7 years (sand) / 10-15 years (AFM) | Complete media change |
Pressure Gauge Guide:
📊 Clean filter baseline: Record pressure immediately after thorough backwash
📊 Backwash trigger: 0.5-1 bar above baseline reading
📊 Maximum operating pressure: 2.5 bar – never exceed
Winterisation (UK Climate):
❄️ Essential winter protection for the HFS-35:
- Turn off pump and fully isolate electrical supply
- Close all inlet and outlet valves
- Set multiport valve to “Winterise” or position handle between settings
- Completely drain filter tank via drain plug (allow extra time due to size)
- Remove drain plug and store securely indoors
- Leave air vent open to prevent vacuum or pressure build-up
- Cover filter with weatherproof cover or relocate to frost-free storage
- Never allow water to remain in filter during freezing conditions
⚠️ Important: Frost damage from residual water is excluded from warranty coverage. Due to the HFS-35’s large capacity, allow adequate time for complete drainage before winter.
🪨 Filter Media Information
Compatible Media Types:
| Media Type | Filtration Rating | Lifespan | Key Benefits |
|---|---|---|---|
| Silica Sand | 20-40 microns | 5-7 years | Economical, proven, readily available |
| Glass Media | 10-15 microns | 10+ years | Finer filtration, lighter weight, eco-friendly |
| AFM (Activated Filter Media) | 1-5 microns | 10-15 years | Exceptional clarity, self-sterilising, reduced chemicals |
| ZeoSand | 3-5 microns | 5 years | Superior clarity, ammonia removal properties |
Media Capacity for HFS-35:
| Media Type | Quantity Required |
|---|---|
| Sand + Gravel | 28 kg sand (0.4-0.8 mm) + 6 kg gravel (2-4 mm) |
| AFM Media | 15 × 21 kg Grade 1 + 8 × 21 kg Grade 2 + 7 × 21 kg Grade 3 (630 kg total) |
AFM Three-Grade Configuration:
| Grade | Bags | Weight | Layer Purpose |
|---|---|---|---|
| Grade 1 (0.4-1.0 mm) | 15 | 315 kg | Primary filtration layer |
| Grade 2 (0.7-2.0 mm) | 8 | 168 kg | Transition/support layer |
| Grade 3 (2.0-4.0 mm) | 7 | 147 kg | Base support layer |
| Total | 30 | 630 kg |
💡 Recommendation: The HFS-35 includes a special AFM diffusor engineered for optimal AFM media performance. Upgrading to AFM provides filtration down to 1 micron, self-sterilising properties, and 10-15 year media life – ideal for commercial and high-end residential applications.
Signs Media Requires Replacement:
- Persistent water cloudiness despite correct chemical balance
- Rapid pressure rise between backwash cycles
- Cloudy water returning during normal filtration
- Filter media particles appearing in pool
- Elevated sanitiser consumption
- Visible channelling or uneven media bed surface
💎 Filtration Performance
| Metric | Value |
|---|---|
| Filter Area | 0.70 m² |
| Filtration Rating (Sand) | 20-40 microns |
| Filtration Rating (AFM) | 1-5 microns |
Micron Rating Guide:
| Rating | Particle Types Removed |
|---|---|
| 40+ microns | Leaves, insects, visible debris |
| 20-40 microns | Sand, grit, visible suspended particles |
| 10-20 microns | Fine particles, some algae spores |
| 5-10 microns | Very fine matter, most algae types |
| 1-5 microns | Ultra-fine particles, bacteria, all algae |
Superior Filtration Design:
The HFS-35’s extended filter bed height delivers almost 50% more media contact time compared to standard filters. Combined with the largest filter area in the range (0.70 m²), performance advantages include:
✅ Maximum flocculation efficiency for finest particle capture
✅ Superior removal of organic matter and suspended solids
✅ Exceptional water clarity and sparkle
✅ Significantly reduced chemical consumption
✅ Extended intervals between backwash cycles
✅ Consistent performance under high bather loads
✅ Commercial-grade reliability for demanding applications
⚙️ Valve Positions & Functions
The HFS-35 accepts a 6-way multiport valve (sold separately) with these functions:
| Position | Function |
|---|---|
| Filter | Normal operation – water flows through media and returns to pool |
| Backwash | Reversed flow flushes debris from media to waste |
| Rinse | Resettles media and clears lines after backwashing |
| Waste | Bypasses filter – water drains directly (for heavy debris removal) |
| Recirculate | Bypasses filter – water returns to pool (for chemical mixing) |
| Closed | Stops all water flow through valve |
💡 Note: The HFS-35 requires a 2½” valve to match its larger connections. Besgo backwash valve fits as standard. Coupling set sold separately. Exclusive Calplas 6-way valves available in automatic or manual configurations.
🎯 Ideal Applications
| Application | Pool Size | Suitability |
|---|---|---|
| 🏠 Large estate/luxury pools | Up to 168,000 L | ✅ Excellent |
| 🏠 Premium residential | 100,000 – 150,000 L | ✅ Excellent |
| 🏨 Hotel/resort pools | Up to 126,000 L | ✅ Excellent |
| 🏢 Health club/leisure centre | Up to 126,000 L | ✅ Excellent |
| 🏫 School/university pools | Up to 126,000 L | ✅ Excellent |
| 🏡 Holiday complex pools | Up to 140,000 L | ✅ Excellent |
| 🏊 Training/competition pools | Up to 150,000 L | ✅ Good |
Best Suited For:
- Large residential pools requiring flagship filtration capacity
- Commercial leisure facilities with high bather loads
- Hotels, resorts, and holiday complexes
- Educational and institutional swimming facilities
- Properties where water quality is paramount
- Installations planning AFM media for superior 1-micron filtration
- Replacement of ageing commercial-grade filtration systems
- New builds requiring long-term, reliable filtration solutions
❓ Frequently Asked Questions
Q: What size pool will this filter handle?
A: The HFS-35 is suitable for pools up to 168,000 litres with an 8-hour turnover, or up to 126,000 litres for optimal 6-hour turnover. With a 21 m³/h flow rate and 0.70 m² filter area, it’s the largest filter in the HFS range, ideal for large residential and commercial pools.
Q: How often should I backwash?
A: Backwash when the pressure gauge reads 0.5-1 bar above your clean baseline. For commercial pools with high bather loads, this may be required several times per week. Residential pools typically need backwashing every 1-2 weeks during swimming season.
Q: What filter media should I use?
A: The HFS-35 accommodates 28 kg sand plus 6 kg gravel, or AFM media totalling 630 kg across three grades (15 bags G1 + 8 bags G2 + 7 bags G3). The integrated AFM diffusor makes this filter ideal for AFM upgrades, achieving filtration down to 1 micron.
Q: How long does filter media last?
A: Sand typically requires replacement every 5-7 years. Glass media and AFM last 10-15 years with proper maintenance. For commercial applications with high usage, inspect media annually and consider more frequent replacement.
Q: What pump do I need?
A: Select a pump delivering 14-22 m³/h for optimal performance. Never exceed the filter’s maximum flow rate of 35 m³/h. Ensure the pump has 2½” connections or use appropriate adapters. Lower flow rates within the range provide finer filtration.
Q: Why does the HFS-35 have larger connections?
A: The 2½” connections (vs 2″ on smaller models) reduce pressure loss at higher flow rates, ensuring the HFS-35 can handle its full 21 m³/h filtration capacity and 35 m³/h backwash rate efficiently.
Q: What warranty is included?
A: The HFS-35 includes a 5-year tank warranty from Calplas. Contact Parts4Tubs for complete warranty terms and conditions.
Q: Is this suitable for commercial pools?
A: Yes, the HFS-35 is designed for commercial applications. It’s suitable for hotel pools, leisure centres, schools, and similar facilities up to 126,000 litres (6-hour turnover). For larger commercial installations, multiple filters may be required.
Q: Is this suitable for saltwater pools?
A: Yes, the GRP construction provides excellent saltwater corrosion resistance. Ensure all connected equipment (valves, fittings, pumps) is also saltwater compatible.
Q: What’s the difference between HFS-30 and HFS-35?
A: The HFS-35 has a larger 960mm tank diameter (vs 840mm), greater filter area of 0.70 m² (vs 0.52 m²), higher flow rate of 21 m³/h (vs 15.6 m³/h), handles pools up to 168,000L (vs 125,000L), and features upgraded 2½” connections (vs 2″).
Q: Is the multiport valve included?
A: No, the 6-way multiport valve is sold separately. The filter accepts Calplas 6-way valves (automatic or manual) and Besgo backwash valves fit as standard. Note: 2½” valve required for HFS-35. Coupling sets required separately.
📑 Downloads & Resources
📄 Calplas HFS Filter Specifications (PDF) – Complete technical specifications for the entire HFS filter range
🏆 Why Choose the Calplas HFS-35
✅ Maximum Filtration Capacity – 0.70 m² filter area with 21 m³/h flow rate handles pools up to 168,000 litres
✅ Flagship Performance – Largest model in the HFS range with 50% more media than standard filters
✅ Industrial-Grade Construction – Hand-laid GRP with steel reinforcement manufactured to EN 13121-3
✅ Upgraded 2½” Connections – Larger ports for superior flow capacity and reduced pressure loss
✅ Extra-Large 355mm Lid – Maximum access for inspection and maintenance
✅ Three-Grade AFM Compatibility – Optimised for advanced media achieving 1-micron filtration
✅ Commercial-Ready – Suitable for hotels, leisure centres, schools, and high-end residential
✅ 5-Year Tank Warranty – Comprehensive manufacturer coverage on the flagship model
✅ Proven Spanish Engineering – Manufactured by Calplas, specialists in professional pool filtration
🤝 Why Buy From Parts4Tubs
✅ UK-Based Company – Local expertise and dedicated support from pool specialists
✅ Fast UK Delivery – Prompt dispatch for commercial and residential projects
✅ Expert Technical Advice – Professional guidance on sizing, installation, and maintenance
✅ Competitive Pricing – Outstanding value on flagship pool equipment
✅ Full Warranty Support – Direct manufacturer warranty handling
✅ Easy Returns – 30-day returns policy for complete confidence
✅ Complete Product Range – Filter media, valves, spare parts, and accessories available
✅ Trusted Supplier – Established retailer of pool, hot tub, and spa equipment
✨ Summary
The Calplas HFS-35 960mm Side Mount Sand Filter is the flagship model in the HFS range, delivering professional-grade filtration for pools up to 168,000 litres. Built with premium hand-laid GRP construction and internal steel reinforcement to EN 13121-3 standards, this Spanish-engineered filter features 50% more media capacity than standard filters, an impressive 0.70 m² filter area, and upgraded 2½” connections for maximum flow efficiency. With a 21 m³/h flow rate and optimisation for three-grade AFM media (achieving filtration down to 1 micron), the HFS-35 is the definitive choice for large estate pools and commercial installations. Supplied complete with pressure gauge, air vent, 355mm transparent lid, and backed by a 5-year tank warranty.
Order today for uncompromising filtration performance in your large pool.











