HEATING SYSTEMS & RADIATORS
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Why you should maintain your closed water systems?
The attitude towards closed water systems has, unfortunately, often been one of ‘fill it and forget it’. When using water in a closed system for either heating or cooling, the temptation may be to leave it off the maintenance schedule; but this may be both a false economy and a recipe for future trouble, as David Randlesome, National Sales Manager, Legionella Services for Legionella risk experts Swiftclean, explains.
A
closed water system is, simply, one which is filled with water for heating or for cooling purposes. Because it is customary to fill
these once and then allow the water to recirculate repeatedly with little significant need for topping up, the water in many systems can actually be quite old and has passed through the system multiple times. Over time, it is possible for the water to pick up a significant amount of impurities. This may be due to the gradual deterioration of the internal surfaces of the system, so that the water may carry rust, corrosion or sludge particles. In hard water areas, the system may also suffer from scale formation. Microbiological fouling can also occur in closed water systems, so, while occupants of a building are not as prone to contracting illness from a closed
Above: David Randlesome, National Sales Manager, Legionella Services for Legionella
system as from a domestic water system, it is still a potential risk to health. If corrosion or other fouling occurs, the system may become sluggish and less efficient; and blockages may occur, causing the system to break down. In heating systems, it is possible for debris from radiators, for example, to circulate through more expensive equipment such as a boiler, and cause extensive damage which may be costly to fix. The water in a closed system should be monitored to detect any of these
problems so that they can be addressed. The absence of maintenance, particularly the failure to spot a small leak, can cause a system to be routinely topped up with raw water which has not been pre-treated. Water treatment is important, to discourage the proliferation of bacteria and to help ensure the longevity of the system. Cleaning the system correctly before commissioning can also help to lengthen
its lifespan. Effective pre-commissioning will ensure that pipework is clean and free from debris and impurities before the system is filled with carefully treated water, so it should be a prerequisite for any closed system. Pre-commissioning cleaning should be carried out in accordance with BSRIA’s Pre-Commission Cleaning of Pipework Systems 6th edition (Superseded) (BG 29/2020) guidance document. With the pipework free from contaminants, the system should operate efficiently and effectively from the outset. A regular treatment and maintenance programme should also be instigated from the start of the system’s lifetime. The cost of this will be minor in comparison with the possible replacement of some or all of the system, which could be required were it to become blocked or damaged by sludge, scale or metal particles. Once in use, the system should then be maintained in accordance with BSRIA
guidance document Water Treatment for Closed Heating and Cooling Systems (BG 50/2021) or with BS 8552:2012 Sampling and monitoring of water from building services closed systems. Code of Practice. These documents are consistent in requiring the regular sampling of the water in a closed system, to allow it to be monitored and treated for the avoidance of biofouling, corrosion and scale. The presence of metal particles in the water can be an early indicator of corrosion; scale build-up can also be monitored; and the water checked for bacteria and biofouling. Water samples should be taken at the same point in the system at regular intervals to gain an accurate picture of the health of the
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system over time. This should form part of your overall water plan for each building. If the presence of biofouling is detected, the water can be treated to safeguard
the health of building occupants. It may be possible to detect from the presence of metal or corrosion when a heat emitter starts to deteriorate, so that it can be replaced without harming the rest of the system. Water treatment can also be adjusted to discourage the formation of scale should higher calcium levels be detected.
In addition to sampling the water, a visual inspection should also be carried out to make sure that it is in good condition, with no leaks which might require more topping up. Regular inspection and testing of the system will also aid the planning of routine ongoing maintenance. Far from being out of sight and out of mind, care and maintenance of the
water in a closed system should be high on the list of regular tasks for every building manager.
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