Why is good filtration more important than shock treatment?
When pool water becomes cloudy, green, or difficult to balance, many owners immediately think of shock treatment as the primary solution. However, in most cases, the truly essential element for maintaining clean and healthy water remains filtration.
Even a powerful chemical treatment can never compensate for insufficient or poorly adapted filtration. A well-filtered pool generally uses less product, remains more stable, and requires far less extensive maintenance.
Filtration: the true heart of the swimming pool
We often hear that:
“Filtration accounts for approximately 80% of water treatment.”
This statement is very close to reality.
The role of filtration is to:
- retain impurities
- eliminate suspended particles
- homogenize the treatment products
- avoid water stagnation
- limit the growth of algae and bacteria
Even with a good disinfectant, poorly circulating water will almost always eventually deteriorate.
What is the real purpose of shock treatment?
The shock treatment is designed to:
- quickly destroy bacteria
- eliminate a high presence of algae
- restoring degraded water
- oxidize organic matter
- quickly restore the disinfection level
This is therefore a one-off solution, and not a normal functioning of the basin.
A swimming pool that regularly requires shock treatments often indicates a deeper problem:
- Insufficient filtration
- filtration time incorrectly set
- poor hydraulic circulation
- clogged filter
- unbalanced water
Shock treatment acts as an “emergency solution”, but it does not correct the real cause of the problem.
Poor filtration promotes all kinds of imbalances
When filtration is ineffective:
- impurities remain in the water
- microorganisms develop more easily
- stagnant areas appear
- the disinfectant becomes less effective
- algae proliferate more rapidly
Result :
- murky water
- deposits
- slippery walls
- excessive consumption of chemicals
- repeated shock treatments
In some cases, the problem simply stems from insufficient filtration time.
The optimal filtration time varies depending on the temperature
A simple rule is often used:
Daily filtration time ≈ water temperature / 2
Example :
- water at 28°C → approximately 14 hours
- water at 24°C → approximately 12 hours
The warmer the water, the faster bacteria and algae develop.
During the summer months, excessively reducing filtration to “save money” can cause rapid water degradation.
Well-mixed water improves the effectiveness of the products
Filtration is not only used to clean water.
It also allows:
- to properly distribute the chlorine or the treatment
- to avoid local concentrations
- to even out the temperature
- to limit dead zones
Even an excellent treatment becomes ineffective if the water does not circulate properly.
The filter plays an essential role
The filtering medium is often underestimated.
Depending on the type of filtration used:
- sand
- filter glass
- cartridge
- diatoms
The filtration fineness varies enormously.
A dirty or saturated filter greatly reduces the performance of the pool.
Some signs of a clogged filter:
- high pressure
- low flow
- persistently cloudy water
- poor suction
- rapid appearance of algae
A simple cleaning or replacement of the filter media can sometimes resolve recurring problems without drastic measures.
Variable speed pumps often improve water quality
Contrary to popular belief, slower filtration can be more effective.
Variable speed pumps allow:
- improved filtration fineness
- a more constant flow
- less turbulence
- reduced electricity consumption
The water passes more gently through the filter, which improves the capture of fine particles.
Result :
- clearer water
- fewer chemicals
- improved pelvic stability
Shock treatment should not become a habit
Frequent shock treatments have several drawbacks:
- overconsumption of products
- high cost
- premature wear of equipment
- significant variations in chlorine levels
- discomfort for bathers
In some cases, this can even further unbalance the water.
A well-designed and well-filtered swimming pool generally requires very little shock treatment.
The importance of water balance
Even with excellent filtration, certain parameters remain essential:
- pH
- TAC
- disinfectant level
- stabilizing
But well-mixed water greatly facilitates the stability of these parameters.
Filtration helps to maintain the overall balance of the pond.
The most common mistakes
Here are the most common mistakes observed in swimming pools that regularly experience water problems:
- Filtration stopped for too long
- undersized pump
- poorly maintained filter
- insufficient backwashing
- poor hydraulic circulation
- reduced filtration time at night
- Cover closed without sufficient circulation
Very often, the problem does not stem from a lack of chemicals, but from a lack of circulation and filtration.
A stable swimming pool uses less product
Good filtration allows for:
- less algae
- less murky water
- fewer corrective treatments
- fewer chemicals
- less spending
It is also a more environmentally friendly and more comfortable solution for users.
Conclusion
Shock treatment remains useful in certain exceptional situations, but it should never replace efficient filtration.
Clean water depends primarily on:
- of good circulation
- of an appropriate filtration time
- of a maintained filter
- of a properly designed hydraulic system
In most cases, improving filtration provides a lasting solution to water problems while reducing maintenance costs.
Before adding more and more chemicals, it is often best to check if the filtration system is actually working optimally.