Pool filtration system buying guide
Patrick, Handyman, Bath11 guides
- Pool basin volume
- Sand filter
- Cartridge filter
- Diatomite filter
- Sock filter
How to choose my pool filtration system?
The water is drawn in via skimmers, passes through filters and is then reintroduced to the pool basin via outlet nozzles.
What are the different types of pool filters?
Swimming pool filter performance is measured by the water clarity it produces, or in other words, the size of particles it's capable of removing.
There are four main types of filters:
- Sand filters are the most common type, offering impressive value for money;
- Cartridge filters, which have an elongated shape, are made of paper or synthetic material;
- Diatomite filters are cylindrical in shape;
- Sock filters are sometimes used on smaller swimming pools.
Each type has its advantages and disadvantages.
How does a sand filter work?
A sand filter consists of a cylinder two-thirds filled with a granular material of an appropriate grain size to produce good filtration.
The size of particles the filter can exclude depends on the grain size of the filter material as well as the rate at which the water passes through it.
Despite the generic name "sand filter", these devices can also contain zeolite or glass beads as additional filter materials.
What's best: sand, zeolite or glass beads?
- Sand: favoured by most pool owners for its low price, ease of use and foolproof maintenance. It's a good idea to include two different grain sizes for optimal filtering - a layer of grain size 2-4mm at the bottom and a layer of 0.4mm on top. It's also possible to get an intermediate grain size of 0.6mm, likewise giving good results. This type of filter provides filtration to a grain size of about 35 microns. Using flocculants can further improve performance.
- Zeolite: a mineral of volcanic origin. Its filtration capacity is far superior to sand - but it's substantially more expensive too. The cost is somewhat offset by the reduced requirement for water treatment products such as clarifiers. The fineness of filtration provided by zeolite makes it a competitor to the diatomite filter. Use and maintenance are identical to a pure sand filter, and the two substances can also be combined. The sand can be replaced with zeolite without modifying your installation.
- Glass beads: a material based on polished recycled glass. Glass beads have only recently come on the market and can be used to improve filtering performance over sand alone and have the advantage of not producing a surface film like sand and zeolite. Washing therefore takes less time, thus saving water.
How does a diatomite filter work?
A diatomite filter is in the form of a cylinder containing a membrane. This membrane contains diatomaceous earth - a white powder derived from microscopic algae fossils.
Why choose a cartridge filter?
Pocket filter, sock filter... What's the deal?
Reserved for above-ground pools receiving occasional use, the pocket filter consists of a cloth pocket or "sock" that is cleaned regularly.
Since it's subject to wear, the sock must also be changed regularly.
The requirement for frequent cleaning can quickly become tedious.
Its fineness of filtration places it at the bottom of the pile compared to the other types of filter.
However, the pocket filter is commonly used in one-piece filtration blocks.
What filtration capacity to choose for your swimming pool filter?
To obtain good quality water, the full volume of your pool should be filtered within six hours maximum, and ideally four.
Calculate the volume of your pool, divide by 4 and add a safety margin of 1.3 to get the minimum flow of your filter (F).
For sand filters, an additional factor must be considered: filtration speed, which must not exceed 50m/h. This dictates the minimum filter area (A) of your filter, where A = F / 50. This in turn dictates the minimum diameter of your filter.
In our case, with a flow of F = 13m3/h, the area must be at least (13m3/h / 50m/h) = 0.26m2, giving a minimum diameter of 575mm.
For those of you who aren't into maths, don't fret, most of the time the filtering area is given by the manufacturer!
Learn more about swimming pool equipment...
How to choose your swimming pool liner?
How to choose your pool cleaning products?
How to choose your pool maintenance products?
How to choose your pool robot?
How to choose your pool cover?
How to choose your pool filtration system?
How to choose your pool heat pump?
How to choose your pool heat exchanger?
How to choose your electric swimming pool heater?
How to choose your pool alarm?
How to clean your pool?
How to filter your pool?
How to cover your pool?
How to heat your pool?
How to secure your pool?
How to choose your pool?
Patrick, Handyman, Bath 11 guides écrits
It's also a family affair. I love nothing more than spending weekends in the workshop with my kids, who have inherited my love of tinkering. We motivate each other and share ideas about different projects - most of which are successful, I'm not shy to admit. But that’s one of the best parts of a DIY lifestyle: working together and having fun doing it.
By the way, should you ever need some advice or guidance, I'm happy to help you, too!