Swimming pool filters

Content

• 1 How to choose the right pool filter 
• 2 What do we use the pool filter for
• 2.1 Parts of the filtration equipment
• 2.2 Filtering materials
• 3 Types of swimming pool filter 
• 3.1 Sand filters
• 3.2 Cartridge Filters
• 3.3 Diatomaceous Filters 
• 3.4 Monoblocs
• 4 How to choose the right pool filter
• 4.1 The flow rate to filter 
• 4.2 Type of pool  
• 5 Sand filter operation

How to choose the right pool filter 

Now it seems far away, but in a few months the good weather will be back, and with it you will have to get your pool ready for the summer. Among other tasks, you will have to check that the filtration system is in good condition, you will surely want to take the first bath of the season with the cleanest water ever! 

This is why it is essential to have a good filtration system. But... You still haven't made up your mind? Do you have some doubts about which filter is the most suitable for your pool? No problem, here are some tips to help you choose the best filter for your pool.

What do we use the pool filter for?

In order to obtain a pleasant water for swimming, with a crystalline aspect, it is necessary, in any type of swimming pool, to submit it to a filtration process. The water, being in the open air, is subject to constant pollution. This contamination comes mainly from microorganisms that are in the air itself and those released by the bathers. In addition, the increase of temperatures that occur in the summer season, facilitates the formation of lives. For all these reasons it is essential to carry out a good maintenance and cleaning of the water. 

There are different types of filters: 

• Sand filters, the most popular as they require little maintenance and offer good quality;
• Cartridge filters, with annually replaceable cartridges and ideal for removable pools;
• Diatomaceous filters, the most expensive option due to their filtration power, containing all types of dirt, including microscopic and impossible to capture by the human eye. 

Parts of the filtration equipment

When we talk about a filtration equipment, we are not only referring to the filter, but it is necessary to install a system composed of a set of elements, if one of them is missing, the filtration equipment would not work properly: 

• A pool pump to move the water from the pool to the filter and return it back filtered. 
• A filter to retain all the particles in suspension in the water. 
• A sump or skimmers where the pump absorbs the water that will drive to the filter. 
• Some nozzles of impulsion by where the water will return to the swimming pool. 

Filtering materials

When the water circulates inside the filter, it encounters a material that retains its impurities, allowing only particle-free water to return to the pool. The filtering material can vary according to its origin, giving more or less quality to the final set. The materials that we can find in the interior of the container of the filter are: 

• Flint: this is a porous material derived from silica. It is an economical option that requires replacement every 4 years. 
• Glass: it is the most environmentally friendly filter media. Made from recycled glass, it is an excellent filter media. It has important advantages over other materials. It is more permeable, removes fine particles, stays cleaner, does not degrade over time and requires less filter loading. In addition, it does not require replacement, it lasts forever.  
• Zeolite: of volcanic origin and fine earth texture. 
• Diatomaceous: it provides a great filtration quality, but its cost is high. 

Types of swimming pool filter

Sand filters

These are the most conventional and require the least maintenance. The water is cleaned by passing through this natural filtering agent. A great advantage that it presents is the durability of the filter besides allowing the backwashing (inverse process to the filtration cleaning and eliminating the impurities of this one). 

In the market we can find these filters with two types of selector valves: with side valve or with top valve. This element allows to choose the different processes of washing, emptying, recirculation and backwashing of the pool. It is advisable to purchase the filters with side valve, as they are easier to access and install. Filters with top selector valve are usually used when the space in which the filter is located is limited, as in the case of in-ground pools. 

Cartridge Filters

Replaceable cartridgesThe system consists of replaceable cartridges that need to be cleaned weekly and replaced approximately every year. The main advantage of the system is easy installation and cleaning. It can be washed with a hose or replaced with a cartridge at a cost of about 10 euros. Its filtration capacity is not as high as sand filters, but is sufficient for small, removable or inflatable pools. 

Diatomaceous Filters

This type of filter is considered to be top of the line. Diatoms are fossilized microorganisms that act as filtering agents, functioning like microponges. With this filter, the quality of the water obtained is excellent, containing the smallest dirt particles. This system has one disadvantage, and that is that it is more expensive than previous filters. This system also has a backwashing system, which also makes it easier to maintain. 

Its filtration system is quite different from that of sand filters: the water passes through diatom-laden filters, whose bodies can be compared to sponges with high filtration efficiency. 

It is the system with the highest final water purity, but also the one that requires the highest investment. 

Monoblocs

These are kits that include the pump together with the filter, which makes the decision easier when choosing a suitable pump for a filter and vice versa. These kits can be with either a sand filter or a cartridge filter. With these, you only need to connect the water inlet and outlet to the filter. 

How to choose the right pool filter? 

When choosing a filter for your pool, the following criteria should be taken into account: 

1. The flow rate to be filtered 
2. The type of pool where the equipment will be installed 

The flow rate to filter 

• The volume 

To know the flow rate, which will determine the size of the filter, you must first calculate the volume of your pool. It's very easy: 

Volume= length x width x average depth 

For example, if we have a 6m x 4m x 1.5m pool, the pool volume will be 36m3. 

• Flow Rate 

You should know that the recommended filtration time is about 8 hours a day, that is, you should have the equipment running for about 8 hours. 

To know the most adequate filter, you must first know the flow rate that you should filter: 

Flow = volume of the pool (water to be filtered) / filtration time (usually 8 hours). 

Let's continue with the example: 36m3 / 8h =4,5m3/h 

The filtration capacity that the filter should give us will be 4,5m3. 

It is important to remember that the pump that drives the water to the filter must be able to move the same amount of water per hour as the filter. If the pump is more powerful, it will send more water than the filter can filter in its time, creating filtration channels within the filter, allowing water to pass through unfiltered. If it were the other way around, by not pumping enough water, the quality of the filtration obtained would be less than adequate. 

If we know the filtration capacity required for our pool, the manufacturer will easily tell us which filter and pump is suitable for our pool. 

For your reference, for residential pools, the most commonly used filters are Ø300, Ø400, Ø500 and Ø600 (millimeters), and pumps from 0.5 to 2 HP. 

Type of pool 

The filter you choose varies according to the type of pool you have and also according to your budget, which will make you decide between low, medium or high range filters. 

• Private pools 

For residential pools, sand filters, ranging from 300 to 600 millimeters in diameter, are the most suitable. Within this group, we can find different types, depending on their manufacture. This factor affects their quality and therefore their price: 

1. Laminated: belongs to the highest range, due to its strength and good performance. 
2. Rolled: We place it in the medium-high range, since it has very good characteristics. 
3. Stainless: Manufactured by stamping stainless steel. 
4. Injected: It is composed of a single piece injected in plastic materials. We would place it in the lower middle range, although it is one of the most widely used. 
5. Blown: Formed by blowing, it is also made of a single piece. We would place it in the lower mid-range, and it is one of the most popular. 

• Small, removable or inflatable pools  

For this type of pool, also for private use, the most recommended filters are cartridge filters, smaller capacity sand filters, and monoblocs or kits that include the pump in the filter itself. 

Sand filter operation

The operation of sand filters is simple but effective: 

The water coming from the pool enters through the filter inlet, passing through the filtering sand until it reaches the base of the filter, where it meets the collectors. 

These are PVC arms with small holes that absorb the filtered water and through the water outlet, it is returned to the pool completely clean.

With the selector valve we can choose the desired function, among them the backwash. This consists of carrying out the inverse circuit to the filtering circuit. 

By means of the pressure gauge located at the top of the filter, you can know the state of the internal pressure of the filter, which tells you when you should perform this cleaning process. The water circulates from bottom to top expelling the particles retained in the previous filtering processes, until they are expelled through the drain outlet. 

We hope this article has helped you to choose the most suitable filter for your pool and if you still have any questions you can always contact us.