Side Stream Filtration Units: DN50, DN80 and DN100 Compared

In modern UK commercial buildings, the protection of terminal units and heat exchangers is paramount to maintaining energy efficiency. Side stream filtration units operate by continuously diverting a small percentage of the total system flow, typically between 5% and 15%, through a high-efficiency stainless steel filter housing containing bag filters or mesh inserts. By doing so, these units capture suspended solids and magnetite that chemical dosing alone cannot resolve. For M&E contractors, installing a dedicated skid-mounted solution is the most effective way to adhere to BSRIA BG29 pre-commissioning cleaning standards and the long-term maintenance requirements outlined in BG50. Our Surrey-manufactured units are designed to handle these rigours with a robust 2-year warranty for peace of mind.

When specifying these systems, it is vital to understand that side stream filtration units are not merely 'add-ons' but are integral to the longevity of the entire plant. Without effective filtration, metallic debris can lead to premature pump failure, localised corrosion, and significantly reduced thermal transfer in plate heat exchangers. By integrating a UKGP side stream filtration skid, engineers ensure that the water chemistry remains stable and that the circulating fluid meets the turbidity targets set by BS 8552. Our units offer a compact footprint, making them ideal for both new build specifications and retrofit projects where plant room space is often at a premium, ensuring that your installation meets the highest industry benchmarks.

Choosing between a DN50, DN80, or DN100 unit depends heavily on the total system volume and the desired turnover rate. A common mistake is undersizing the filtration capacity, which leads to inadequate debris removal and increased pressure drops across the system. Conversely, oversizing can lead to unnecessary capital expenditure. At UKGP Industrial, our side stream filtration units start from £6,800+VAT, providing a cost-effective yet premium engineering solution for the UK market. With a typical lead time of 6-8 weeks for made-to-order skids, we work closely with procurement leads to ensure that project timelines are met without compromising on the quality or the technical specification of the peripheral components.

The DN50 side stream filtration units are the workhorses of the mid-sized commercial sector, typically suited for systems with a total water volume of up to 50,000 litres. These units are frequently specified for schools, regional office blocks, and healthcare facilities where the primary goal is to maintain water clarity without needing the massive flow rates of industrial-scale plant. A DN50 skid provides a manageable balance between filtration surface area and physical footprint. It is essential to ensure that the pump selected for the skid can provide the necessary head to overcome the resistance of the filter bag as it becomes laden with debris, a factor our engineers consider in every made-to-order UKGP assembly.

When comparing the DN50 to larger models, the primary advantage is the ease of maintenance and the lower cost of consumables. The filter bags used in these side stream filtration units are readily available and can be changed quickly by on-site FM teams without shutting down the main system. This 'offline' maintenance capability is a core benefit of the side-stream approach compared to full-flow filtration. Despite the smaller pipework, our DN50 units are built to the same exacting standards as our larger models, featuring high-grade stainless steel housings and integrated bypass valves. This ensures that even in smaller installations, the water quality is managed with technical precision and professional-grade hardware.

For contractors looking to stay within budget while meeting CIBSE recommendations for water quality, the DN50 unit offers an excellent entry point. Pricing for these bespoke skids is competitive, and the ROI is often realised within the first two years through reduced chemical usage and lower energy bills. If you are specifying for a project with a moderate heat load, requesting a quote for a DN50 UKGP unit will ensure you receive a skid that is perfectly tailored to your system's flow requirements. Remember that our lead times of 6-8 weeks allow for precision manufacturing in our Surrey facility, ensuring that every weld and component meets our rigorous internal quality control standards before dispatch.

As system volumes increase toward the 100,000-litre mark, the DN80 side stream filtration units become the preferred choice for consulting engineers. These units offer a significant increase in flow capacity over the DN50, allowing for faster turnover of the system water. This is particularly important in older systems undergoing refurbishment where the initial debris loading might be high. The DN80 specification provides a larger filter housing, which translates to a greater dirt-holding capacity. This means less frequent bag changes and more consistent performance during the crucial weeks following a system flush or chemical treatment, helping projects stay on track for handover and BSRIA compliance.

The DN80 units are often the 'sweet spot' for large residential developments and high-rise office towers. At UKGP Industrial, we ensure that these units are structurally reinforced to handle the increased flow velocities and pressures associated with larger commercial circuits. When considering the move from DN50 to DN80, engineers must evaluate the space available for the skid. While the footprint is slightly larger, the benefit is a significantly more robust filtration process that can catch finer particles before they settle in low-flow areas of the building's pipework. Our DN80 side stream filtration units are designed to be intuitive for facility managers, with clear labelling and high-quality gauges as standard items.

From a procurement perspective, moving to a DN80 unit is a proactive investment in the building's infrastructure. By ensuring the side stream filtration units are adequately sized for the larger pipe diameters and flow rates, you reduce the risk of catastrophic system fouling. At UKGP, we provide full technical data sheets for our DN80 skids to assist you in the CIBSE design process. These units carry our standard 2-year warranty and are manufactured to order in the UK. Contact our sales team for current pricing on DN80 units, and we can provide a detailed breakdown of the technical advantages this specific diameter provides for your current HVAC project or mechanical plant room upgrade.

For the largest district heating schemes, industrial process cooling, and massive multi-use developments, the DN100 side stream filtration units are the industry standard for high-performance protection. These units are capable of processing significant volumes of water, ensuring that even in systems exceeding 150,000 litres, the entire volume is filtered multiple times per day. The DN100 specification features the largest filter housings in our standard range, designed to accommodate high-capacity filter bags or multi-bag arrangements if required. This ensures that pressure drops are kept to an absolute minimum even at high flow rates, preserving the hydraulic balance of the main system while providing maximum debris capture.

In these large-scale applications, the cost of equipment failure is astronomical. Therefore, the specification of a DN100 side stream filtration skid is a critical risk-management strategy. These units are often paired with our air and dirt separators to provide a comprehensive water treatment solution. The DN100 units from UKGP are built with heavy-duty frames and high-efficiency pumps that are designed for continuous 24/7 operation. We understand that in industrial environments, reliability is non-negotiable. That is why our DN100 side stream filtration units undergo rigorous pressure testing and quality checks before they leave our factory, ensuring they are ready for immediate integration into your primary headers or bypass loops.

While the initial investment for a DN100 unit is higher, starting from £6,800+VAT depending on the specific pump and control options selected, the long-term savings in plant maintenance are substantial. By preventing the accumulation of sludge and magnetite in large-bore pipework, these units keep the system running at peak efficiency, which is essential for meeting modern sustainability and carbon reduction targets. Our 6-8 week lead time for these made-to-order units ensures that even the most complex bespoke requirements are met with precision. For consultants designing large-scale hydronic networks, the DN100 skid is the ultimate choice for technical reliability and BSRIA BG50 compliance, providing a future-proofed solution for the building's life cycle.

Comparing side stream filtration units requires a deep dive into the hydraulic characteristics of your project. The DN50 is perfect for velocity-controlled smaller loops, whereas the DN80 and DN100 are better suited to systems where high mass flow rates are the norm. One must consider not just the pipe size but the turnover rate required to meet BSRIA water quality standards. If the system is prone to high levels of oxygen ingress or has a history of corrosion, opting for a larger unit like the DN100 can provide the extra filtration 'muscle' needed to keep the water within specified limits. All UKGP units are compatible with various micron-rated bags, allowing for staged cleaning from 50 microns down to 1 micron.

Another vital comparison point is the pump head. Each of our side stream filtration units is fitted with a pump specifically matched to the skid's internal resistance and the pipe diameter. A DN100 unit will naturally require a more powerful motor than a DN50, which impacts the electrical design of the plant room. However, at UKGP, we use high-efficiency pumps to ensure that the electrical load is minimised. Our technical team is available to help you compare these specs in detail, ensuring that the unit you specify doesn't just fit the pipework, but actually performs the task of protecting your plate heat exchangers and dosing pots effectively. We focus on providing a solution that is technically sound and commercially viable for the UK market.

In summary, the choice between DN50, DN80, and DN100 side stream filtration units should be driven by the total system volume and the specific debris risks associated with the building's age and use. With pricing starting from £6,800+VAT and a robust 2-year warranty, UKGP Industrial provides the clarity and reliability needed for high-stakes M&E projects. Our Surrey-based production facility is geared toward providing custom solutions that larger, generic suppliers cannot match. By choosing a UKGP skid, you are opting for a product that is designed by engineers, for engineers, with a 6-8 week lead time that respects your project's critical path and the requirements for high-quality, BSRIA-compliant water treatment.

Proper installation of side stream filtration units is as important as the selection of the unit itself. For optimal performance, the skid should be installed across the flow and return headers, usually in a location with the highest pressure differential, or with its own dedicated pump as per the UKGP standard design. This ensures a consistent flow through the filter media regardless of the main system's demand. During the commissioning phase, following BSRIA BG29 guidelines is essential. The side stream unit should be brought online as early as possible to capture any residual construction debris or flash rust that could damage sensitive components like control valves and meters, ensuring a smooth handover to the client.

Maintenance access is another critical factor. When installing DN50, DN80, or DN100 side stream filtration units, ensure there is sufficient clearance to remove the filter basket and change the bags. Our UKGP skids are designed with this in mind, featuring ergonomic heights and accessible valve arrangements. Regular monitoring of the pressure differential gauges will tell the FM team exactly when a bag change is required. By implementing a strict maintenance schedule, the system efficiency remains high and the circulating water stays clean, fulfilling the requirements of BS 8552 for water sampling. A well-maintained filtration unit can extend the life of the entire HVAC system by decades, making it a highly cost-effective addition to any plant room.

Finally, always ensure that the side stream filtration units are integrated with the broader water treatment strategy, including chemical dosing and deaeration. A UKGP skid works in harmony with our dosing pots and air & dirt separators to provide a multi-layered defence against the common causes of HVAC failure. If you are ready to specify a unit for your next project, our technical team in Surrey is standing by to provide bespoke drawings and quotes. With our 2-year warranty and commitment to British manufacturing quality, you can be confident that a UKGP side stream filtration unit is the right choice for your building's long-term health and efficiency. Request a quote today to secure your production slot within our 6-8 week manufacturing window.