AQUA-SPAZIO

SWIMMING POOL DESIGN CONSIDERATIONS

When designing an outdoor swimming pool in the UK, important technical considerations include legal and regulatory compliance, structural integrity, efficient heating and insulation, water treatment and filtration, and effective drainage. Careful planning is essential to ensure the pool is safe, durable, and cost-effective to operate in the UK climate. 

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Planning and regulations

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• Permitted development rights: Most outdoor domestic pools do not require planning permission, as they are often covered by permitted development rights. However, they must adhere to strict limits, such as not covering more than 50% of the curtilage area, being single-storey, and not being located in front of the house's principal elevation.

• Building regulations: Building regulations approval is generally not required for uncovered, unheated, and unenclosed outdoor pools. However, if the pool is enclosed or an accessory building (like a plant room) is constructed, it must comply with Building Regulations, particularly regarding electrical installations and energy efficiency.

• Special areas: Properties on designated land, such as Green Belts, National Parks, Conservation Areas, or those with listed buildings, often have restricted permitted development rights and will likely require full planning permission.

• Positioning: Plan the pool's location based on factors like sunlight exposure, prevailing wind direction, and proximity to the house for convenience and services. Avoid locating the pool in areas that will carry dirt and debris into the water. 

Structural considerations

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• Excavation and foundation: Conduct a thorough site survey to assess soil conditions, ground stability, and the presence of utilities. Ensure adequate access for machinery and proper excavation. The pool's reinforced concrete shell or liner must be constructed to withstand ground pressure and prevent water leaks.

• Construction materials: Common options for the pool shell include reinforced concrete, fibreglass, or vinyl liners, each with different durability, customisation, and maintenance requirements. Surrounding paving or decking should be chosen for safety, durability, and aesthetics. 

Heating and energy efficiency

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• Extended season: Given the UK climate, effective heating is crucial for extending the swimming season beyond the summer months. Insulation is essential for retaining heat and reducing running costs.

• Heat pumps: Air source heat pumps (ASHPs) are a popular and efficient option for heating outdoor pools. They are available in various outputs (kW) and use electricity to extract heat from the outside air, offering reduced running costs compared to other methods.

• Solar heating: Solar thermal panels can contribute to heating costs, but their effectiveness depends on sunlight availability.

• Pool covers: A high-quality, insulated pool cover is one of the most effective ways to retain heat and reduce running costs by minimising evaporation. Covers also help keep the pool clean. 

Water treatment and circulation

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• Filtration: A well-sized pump and filter system is necessary to circulate and filter the water effectively, removing debris and maintaining clarity. The plant room housing the equipment needs to be adequately sized.

• Water chemistry: Regular testing and balancing of water chemistry is vital for bather safety and equipment longevity. Key parameters to monitor include chlorine, pH, and alkalinity.

• Chemical alternatives: While chlorine is a standard disinfectant, alternative systems like ultraviolet (UV) sterilisers and mineral water systems can provide a less chemically intensive swimming experience. 

Drainage

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• Poolside drainage: Install separate drainage channels around the pool surround to prevent surface water from entering the pool. This is a requirement under UK safety standards (BS EN 15288-1).

• Overflow: Plan for managing pool overflow and spills, ensuring water is directed away from the pool area and surrounding structures. Proper drainage also protects the pool structure from external pressure caused by a high water table. 

Safety and maintenance

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• Safety barriers and covers: To prevent accidental drowning, especially involving young children, consider installing security features like fencing with a lockable gate, a purpose-made safety cover, or a certified alarm system.

• Signage: Clearly mark water depths and provide safety signs where necessary, for example, indicating no diving areas or slippery surfaces.

• Winterization: For pools that are not heated year-round, proper winterization procedures are critical to prevent freeze damage to the pipes, shell, and equipment.

• Chemical storage: Ensure pool chemicals are stored and handled safely in accordance with supplier instructions.

When designing an indoor swimming pool in the UK, technical considerations are paramount to ensuring a safe, hygienic, and energy-efficient facility. Key areas include environmental control, water treatment, structural integrity, and the layout of the plant room, all of which

must comply with current UK regulations and best practices. 

Environmental control and energy efficiency

High levels of moisture and chemicals inside an enclosed pool hall can cause significant damage to the building fabric, leading to mould, condensation, and corrosion. An effective environmental control strategy is crucial. 

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• Dehumidification and ventilation: A high-performance HVAC (heating, ventilation, and air conditioning) system, specifically designed for indoor pools, is essential. It must manage air temperature and relative humidity (RH), typically keeping the RH between 50% and 60%.

  • Air-to-water temperature differential: The system should maintain the air temperature at least 1°C warmer than the pool water temperature. This helps reduce evaporation and associated running costs.

• Insulation: The building fabric requires robust insulation and a continuous vapour barrier to prevent moisture from reaching cold surfaces, which would cause condensation.

  • Building Regulations Part L: The pool shell itself must be well-insulated to a U-value of 0.25 W/m²K or less.

  • Thermal breaks: All windows and doors must incorporate thermal breaks to stop cold from being transmitted through the frames.

• Heat recovery: To improve energy efficiency and lower running costs, a heat recovery system should be incorporated. This can recover heat from the dehumidification process to warm the pool air or water.

• Pool covers: An insulated pool cover is one of the most effective ways to reduce evaporation, significantly cutting heat loss and humidity levels when the pool is not in use. 

Water treatment and quality

Maintaining safe and hygienic water requires sophisticated treatment systems, especially for public use, where standards are more stringent. 

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• Filtration: A circulation pump and sand filter system are standard requirements. The size of the filter should be adequate for the pool's volume to ensure effective and hygienic filtration.

• Disinfection: Automatic dosing systems are used for sanitation. These systems manage the levels of disinfectants, most commonly chlorine, and control the water's pH.

  • PWTAG Code: The Pool Water Treatment Advisory Group (PWTAG) sets the UK standard for water quality. This requires maintaining specific chemical parameters, including free chlorine, combined chlorine, and pH levels, within tight limits.

• Secondary disinfection: To reduce the dependency on chemicals, systems like UV or ozone can be used alongside traditional chlorination.

• Water balance: Regular testing is needed to monitor for total dissolved solids (TDS), alkalinity, and calcium hardness to prevent corrosion or scale buildup. 

Structural design and building materials

The structure must be capable of withstanding heavy loads and a permanently warm, humid, and corrosive atmosphere. 

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• Pool construction: Common options include:

  • Concrete: Highly durable and offers complete design flexibility. Requires meticulous waterproofing.

  • Stainless steel: Lightweight, hygienic, and offers faster installation, making it suitable for rooftop or upper-level installations.

  • One-piece fibreglass: A quick and efficient option for standard pool shapes.

• Finishes: Internal finishes must be non-hygroscopic (not absorbent), corrosion-resistant, and suitable for the environment. Examples include waterproof render and tiling.

• Glazing: All windows should be sealed double-glazed units with thermally broken frames. Recessed windows should be avoided to prevent condensation.

• Access: Sufficient space must be provided for access around the pool for cleaning and maintenance.

• Drainage: The pool surround should have appropriate falls and drainage channels to collect surface water and return it to the filtration system. 

Plant room

The plant room houses all the mechanical and electrical equipment and should be designed with safety and accessibility in mind. 

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• Location: The plant room should be close to the pool to minimise service runs and system losses. It should not be located near bedrooms due to noise and vibration.

• Size: The room must be large enough to provide ample access around all equipment for maintenance and future replacement of bulky items, such as filters.

• Safety features:

  • Ventilation: The plant room requires adequate ventilation, with separate, robust ventilation for chemical storage.

  • Drainage: Emergency drainage should be installed.

  • Emergency equipment: A drench shower, eyewash station, and safety signage are necessary, especially when handling chemicals. 

Legislation and guidance

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Design and construction must adhere to relevant UK legislation and industry guidance:

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• Building Regulations: Compliance with all parts, especially Part L (Conservation of Fuel and Power) and those governing accessibility, is mandatory.

• Health and Safety Executive (HSE): Public-use pools must follow HSE guidance to ensure the health and safety of users and staff.

• PWTAG Code of Practice: The industry standard for pool water quality management and testing.

• Sport England Design Guidance: Provides best practice design recommendations for sports facilities, including swimming pools.