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Sidestream Systems for Building Services

A sidestream filter is a filter system designed to condition a closed loop system over time by capturing suspended solids and reducing the accumulation of settled solids in critical areas. The filter system normally comprises of a filter housing, cartridges and pressure reading instrument. Within the Building Services sector sidestream filters are recommended on LTHW, CHW and Condenser circuits to fall in line with BSRIA guidelines. The BSRIA BG50 guidelines strongly recommend that sidestream systems should be installed on all systems over 2500 litres.

What benefits can a sidestream filter bring to my system?

Closed loop systems rely on water as a medium of temperature regulation within closed spaces. The nature of closed systems means they are susceptible to solids deposition and fouling which can mean increased energy costs and an environmentally suspect facility. Our experience within building services has highlighted the culpability of fouled valves as a major cause of erratic temperature control within buildings, side stream systems can help overcome this problem by capturing the contamination before they foul critical system components.

The sidestream filter systems when included into a water treatment programme brings many long term benefits such as reducing the risk of under deposit corrosion and allowing for the removal of debris and dirt that absorb and reduce the effectiveness of biocides introduced into the system to treat biofilms and bacteria.

A correctly installed and sized side stream system can protect closed loop systems from these problems by ensuring a low concentration of solids within the recirculating water. The grade of filtration cartridge used can be changed over time to polish the system water. The early installation of filtration systems during the commissioning period is also recommended as it helps to maintain water quality. Side stream systems are relatively straightforward to install and cost effective and because the units are operating on a side stream basis the blockage of the side stream filter will not impact on overall system performance.

How does a side stream filter work?

Sidestream systems are sized to accommodate 5 -15% of the system flow rate with the complete system volume passing through the filter at least once every 24 hour period. The sidestream method of cleaning a system serves as an alternative to a balanced flush and allows for solid particles to be removed over an extended period, used within a wider water treatment strategy sidestream filtration will ensure that the system is maintained in a clean condition and will also prolong the life of the system through the control of corrosion and fouling.

Post commissioning period, sidestream filter units are sized to capture particles in the 20 micron range but the grade and type of filter media can vary depending on the nature and sizes of the particles to be removed in the system. Particle removal grades of sidestream filtration systems normally range between 50 microns and 5 microns. Industrial Filtration recommends that cartridge filters are used on sidestream systems due to the superior efficiency they offer against bag systems .

The sidestream unit is installed across the main system pump with sidestream inlet connecting to the line downstream of the pump and the outlet of the sidestream connecting to the upstream line of the main pump. The filter system should be fitted with pressure gauges or as recommended by Industrial Filtration differential pressure gauges to allow for visual indication of when the filters should be changed out. The filters should be changed out once a differential pressure of 1.5barg is achieved this allows for maximum cleaning efficiency and ensures that the media does not become microbiologically contaminated due to blockage. We also recommend that the sidestream filter system is fitted with an automatic vent valve to ensure that air and other gases generated in the system are periodically removed.

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