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Article published in Piscinas Hoy magazine, March/April 2020 edition

Do all filter glasses have the same origin and characteristics?

One of the most delicate and relevant processes in the maintenance of our pool is water filtration. It is a function of exclusively mechanical nature, which directly influences the characteristics and purity of the water with which we will be in contact. We can define it as the process of retaining unwanted particles of various kinds by a filtering mass, in which the grains act as a mesh that retains the particles between the microchannels generated.

In the market we can find a wide selection of filter media, being the silica sand the most traditional and extended option thanks to its high filtration power at the beginning of its useful life, as well as its low cost.

However, for some years now, sand based on recycled glass has emerged as the preferred alternative for consumers, gaining ground and market share. So much so that some of the international manufacturers and distributors only offer glass sand in their catalogues. But what are the reasons for the increase in demand?

There are two main reasons for the boom in this filter medium. On the one hand, the high durability it offers, much higher than that of silica, since it needs to be replaced long before it has completely lost its filtration capacity due to the compaction and clogging produced by the colonization of bacteria on the surface of its grains. These bacteria generate a substance called Biofilm in order to protect themselves from the chlorine that tries to eliminate them, and it is this substance that agglomerates the grains until it suppresses their initial filtration capacity. So much so that a large part of the chlorine used in the pool is destined to eliminate the Biofilm present inside the filter. However, the glass grains have a flat face geometry without imperfections, which reduces the possibilities of generating Biofilm (since the bacteria cannot adhere to the grain), which notably increases the longevity of this medium.

On the other hand, we must point out the direct economic savings provided by glass, which can be divided into three sections:

  • Water consumption thanks to the reduction of necessary backwashing, since the absence of Biofilm and grain compaction increases the filter’s retention capacity.
  • Electrical energy consumption due to the lower consumption of the pump. All the microchannels of the filter remain open due to the absence of Biofilm and compacting effect.
  • Chemicals, due to the lower presence of bacteria in the filter.

So far the main reasons for the increased consumption of glass sand compared to traditional silica sand, but are all glass sands the same? Although there are technical characteristics that differentiate some manufacturers from others, there is a fundamental feature that allows us to distinguish two groups: the origin of the glass.

Glass sands have their origin in the recycling circuits, which leads to the appearance of different qualities, performance and degrees of hygiene. On the one hand we find those coming from the urban recycling circuit, composed of bottles, jars and waste from a waste recycling container. Due to its composition, in this group it is probable the presence of bacteria and improper that can migrate to the filtered water with which we will enter in contact in our swimming pool. Therefore, it is important to ensure that the filtering glasses of this category have gone through an optimal washing process that ensures the total absence of these contaminants.

On the other hand, we have the glass with origin in the flat glass circuits, that is to say, leftovers from the window industry and similar, which due to their trajectory have not been in contact with contaminants of any kind. In this case, it is not necessary to subject the glass to washing processes, thus significantly improving the product’s ecological footprint.

Due to the importance of the filtration process in our pool, it is essential that before replacing our filter media we carefully study the different alternatives offered by the market, as well as the different degrees of performance, savings, purity, safety and durability certified by each manufacturer. Only in this way will we ensure that our pool water meets the standards of transparency and hygiene that we deserve.