Pool/ Spa: all about water filtration

Did you know that the filtration of your pool or spa water has a strong impact on its quality? Indeed, if filtration retains polluting agents and insoluble particles, it facilitates disinfection and thus allows a faster and more effective action of the chemicals. Thus, chemical treatments are only 20% responsible for maintaining balanced water! This is good news for the planet and for your budget, but be careful to choose the right system and to apply the right filtration rules.

filtration acts on pool/spa water quality

Various filtration systems

There are three categories of filters. The size of the filter depends on the volume of the pool or spa and its characteristics (use, environment, etc.). Your choice must be made on two criteria: the desired filtration fineness and the type of maintenance operation.

  • Sand or glass filter
    • These filters are recommended for large pool volumes because large volumes of water can be filtered quickly. The filtration fineness is a little less fine than the other systems but by adding a flocculant, the filtration fineness is significantly improved.
  • Cartridge filter
    • If the cartridge filter allows a fairly precise filtration of the water, the volume of water treated is slower than a sand system. This equipment should be chosen for a medium to small pool with low calcium content. The manual maintenance is very easy with a water jet and the replacement of the cartridge remains occasional (according to your use).
  • Diatomaceous earth (DE) filter
    • It is the most precise model in terms of filtration fineness, but it represents a more important investment at the time of purchase but also due to the more frequent replacement of the filter.

Basic rules to know the filtration time of water

The filtration time of a pool or spa is largely related to the water temperature. Indeed, the warmer the water, the more microorganisms (algae or bacteria ) develop. Therefore, it makes sense to filter longer when the water is warmer.

The rule to remember is to set the filtration time equal to the water temperature divided by two. If for example your pool is at 28°C, the optimum filtration time will be 14 hours per day.

  • If you are not using a heat pump, the filtration time will vary according to the season.
  • In water below 10°C (active wintering), the growth of microorganisms is greatly slowed. So you can just filter for two to three hours a day.
  • If you have a liner or membrane and are using chlorine pebbles in the skimmer, you will need to turn on the filtration until the pebble dissolves to avoid discoloring your liner.

Factors to consider to optimize the filtration time

  • Number of swimmers
    • Swimmers bring a lot of pollution into the water, especially if they haven't showered before their swim! You should increase the daily filtration time if you know that the number of bathers will be important. And lower it the next day.
  • Your pool/ spa environment
    • Another important factor that affects filtration time is the pool environment. If your pool is surrounded by trees and vegetation, it is easy to understand that for the same pool size, temperature and use, an indoor pool or spa will require much less daily filtration time.
  • Hydraulicity
    • The hydraulics of a pool is the way in which the water circulates naturally or mechanically, through circulation nozzles for example.
    • if the water circulation is not good, the water is not well mixed in certain areas of the pool. This creates areas where algae growth will be more important.
    • A pool with good hydraulics will need less filtration time so that the disinfecting power of the water reaches every corner.

When to activate the water filtration?

To activate filtration effectively, here are a few principles you need to remember:

  • Daytime activationit is better to activate the filtration during the day for two reasons: under the effect of the heat, the water evolves rapidly. As mentioned earlier in this article, filtration slows down the alteration of the water and will be all the more effective. Secondly, it is preferable to activate it during swimming hours (or just after swimming) to quickly recover a maximum of pollution brought by bathers in the filter.
  • Two-stage filtrationA two-stage filtration (not continuous) will be more efficient because it allows to collect more impurities on the surface before they fall to the bottom of the water. Indeed, once at the bottom, the residues (leaves, insects) will have to be removed manually or with a robot.

To conclude

We can never repeat it enough, a good filtration is essential to maintain a healthy and clear water. It is necessary to choose the system the most adapted to your pool and to the frequentation of your pool. To save energy, remember the basic rule of filtration time: water temperature / 2.