A Brief History Of Swimming Pool Filtration

 pool filtration
The swimming pool industry has surely come a long way since I was young, especially in the past couple of years. And as much as the pool industry has been associated with the color blue, in recent years, they are going green…and so are their products.

To this day my father reminds me of what the pool industry was like over 40 years ago. He tells me about these ten-foot tall, monstrous sand and gravel filters with huge levers for backwashing and waste. He painted a pretty vivid picture for me and until recently I could only imagine what those things were like.

I finally got to see one of them up close and personal and it is a perfect example of just how far this industry has come. In every aspect of the word, the pool industry took an innovative turn into the modern world of technology and efficiency. Today we have 3 completely different types of filtration methods and media for swimming pools and you don’t need a 10 ft. tall metal tank to filter them. But it wasn’t always this way…

About 50 to 60 years ago, basically all swimming pool filters were sand and gravel filters consisting of multiple layers of sand and gravel. In order to capture a significant filter area, these filters had to be extremely large which also made them very expensive, initially. They also only had a 1 to 2 week water cycle and had to be backwashed very often. On a positive note, sand and gravel filters were an extremely effective way to filter your water. They were also just as durable and generally trouble-free.

Sand and gravel filters are rarely seen today but every so often I run into one. They are simply too big in a world where innovation is pushing compact design.  Their high cost and size render them an impractical form of filtration.

Today’s version of the older sand and gravel filters are the high-rate sand filters – same concept, different design. High-rate sand filters are essentially just an updated and modernized version of the sand and gravel filters. They use a single layer of very fine sand and are significantly smaller in size, requiring only about 15% of the space required for a sand and gravel filter. This compact size, although more convenient and cost effective, requires about 40% more water due to the fact that they must be backwashed more often. They also filter less particles than that of a sand and gravel filter due to their high pressure rate. This high rate filtration allows smaller particles to force their way through the sand and back into the pool water where the slow moving water of a sand and gravel filter trapped these particles, which allowed for better filtration. High rate sand filters only filter about 50-100 microns on a regular basis but can filter down to 25. Sand and gravel filters can filter consistently between the 8-10 micron range.

Both Sand and gravel filters and high-rate sand filters could virtually last you forever. But the sanitary aspect of a media sitting inside a filter designed to capture debris and bacteria became something of a health concern. Generally the sand should last about 10 years and then need to be replaced.

Eventually D.E. or Diatomite filters were introduced and sand filters took a backseat to the unmatched filtration qualities of these filters. Unlike the permanent media of a sand filter, D.E. filters require a diatomite filter media that is applied to the internal filter elements at the beginning of every cycle and removed with the backwash water at the end of the cycle.

Where sand filters lacked, D.E. filters excelled in every aspect. Their extremely compact size and ability to filter particles as small as 2 microns made D.E. filters the future of filtration in the swimming pool industry. D.E. filters are still the most effective filtration units today but at the time they still required backwashing. Backwashing is an extreme waste of water and would require filling the pool with fresh water more often. This affects the water bill as well as a pool’s water chemistry.

Cartridge filters were soon introduced for residential purposes with the ability to be taken out, washed off and put back. Although this was more work than turning a valve on sand and D.E. filters, it did not require backwashing and was relatively easy to do.  Cartridge filters also filter smaller particles than high rate sand filters and are the most compact in size.

Nowadays filters have taken the quality of a D.E. filter and combined it with the convenience of a cartridge filter. Not only do the new D.E. Cartridge filters not require backwashing but they do not need to be cleaned as often as single cartridge filters and they have the same filtration qualities of a standard D.E. filter. It’s the best of both worlds in a compact, efficient design.

From the filters of old to the filters of new, these filtration methods have slowly evolved over the years into the compact, efficient, green products of today’s swimming pool industry. With the durability and quality of older filter models molded with the compact and efficient designs of todays, swimming pool filtration has truly come a long way.

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