How Pool and Hot Tube Filtration Systems Work

by Pool Builders on 12-22-2010 in Articles

Is there any better way to beat the heat then to take a dip in a crystal clear, cool swimming pool? Or is there a more ideal way to relax than sinking into a warm, comfortable hot tub? I think not! But if your pool looks like a swamp, or your hot tub looks like witches brew, then the best you're probably getting is a miserable cold shower. With the proper pool and hot tub filtration systems and a little maintenance you can avoid these types of mishaps and disasters.

All pools and hot tubs have filtration systems. If yours doesn't, then make a phone call to the person who built or installed your pool or hot tub and shake them vigorously, because it's obvious why your water is dirty. Jokes aside, a common reason why pools and hot tubs become dirty is simply because its filtration system hasn't been cleaned or maintained in awhile. For this reason, it's important to know which kind of filtration system your pools and hot tubs have and what kind of upkeep they require.

The three most popular types of filtration systems for pools and hot tubs are diatomaceous earth (DE), sand and cartridge filters. Generally DE filtration systems are used in pools, and are considered one of the best. DE is a siliceous sedimentary rock that is mined and processed into a fine powder. These particles are very pours and thus giving them an abrasive feel. It is for this reason that DE is most commonly used in water filtration systems.

In pool filters, the DE powder is typically mixed with water and dumped into the skimmer where it is then taken to a filtration tank, where inside, is a network of screens. The DE then coats these screens, also known as grids, where it then performs its act of filtering the water. Once the water has been separated from the dirt by passing through the network of DE coated screens, it is then returned to the pool. As the DE filters out more dirt, the water is unable to pass through the filtration system as quickly, causing the pressure inside the filtration tank to rise. Once the take is elevated to an indicated pressure, it's time to clean it out. This process is generally known as "backwashing" which is just running the filtration system in reverse. The only difference is that the water is dumped outside of the pool instead of being returned to it. After backwashing is complete the backwash valve is closed and the filtration valve is reopened for normal circulation; at which point more DE needs to be mixed with water and added to the skimmer to replenish the DE that was flushed with the dirt and debris during backwash. DE is considered the best because it can filter out particles as small as 4-5 microns. Just to exemplify how small that is, a micron is also known as a micrometer. If you drew a line with a ruler 1 millimeter long and divided that line into 1000 equal length segments, each segment would be 1 micrometer (or micron) in length. That's pretty small!

The next most popular filtration medium for pools is sand. These filtration systems are based off of the way rain water is filtered by the ground. Unlike the DE filtration systems, you don't have to add or replenish sand to the filter through the skimmer. Tightly packed sand is contained with the filtration tank, where the water is pushed through from the top, and sent back to the pool at the bottom. As the water is pushed through the sand, the sand catches and prevents any dirt or debris that has not been dissolved from passing through. As the sand filters more debris the pressure in the tank begins to raise, just like in the DE filters. Backwashing is preformed in a very similar manner. Water is pumped in the reverse direction, agitating the filtration sand and separating it from the debris. The debris is flushed and the filter sand settles and is repacked upon normal circulation. Sand filters are generally used in large pools, like those seen at public parks or fitness centers because the filter medium (i.e. sand) hardly ever needs to be replaced. And with regards to particle size, all three do an exceptionally well, but as compared to cartridge and DE filters, sand gets the bronze medal. This brings us to our third kind of filtration system.

Cartridge Filters are used in both pools and hot tubs, but are typically seen in hot tubs and smaller systems like portable pool vacuums. These filters are generally made of woven polypropylene (a type of polymer) threads. They filter the water the same way a coffee filter works and they're efficiency is dependent on how tight these threads are woven, and how think these threads are made. These threads are able to filter a wide range of particle sizes, ranging between 2-10 microns. They have the potential to outperform DE filtration systems, but not without a big price tag. The real attractive part of owning a cartridge filtration system is how easy they are to clean; no backwashing. To clean these filters all you need to do is remove the cartridges from the tank and spray them off with a hose. A decent reusable cartridge will last around 5 years, making it a fairly economical medium for filtering pools and hot tubs.

Pools and Hot tubs are perks of life that do come with some responsibility. It's important to remember to clean your filters appropriately and regularly to avoid having to spend more time cleaning yucky stuff like algae. Obviously these topic points are generalized, so it is important that you contact and converse with a local professional if there is any confusion. Stay around and look out for more tips on how to keep your pools and hot tubs clean.

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