- Presence of green algae

​- Over-stabilisation

The stabiliser rate in the pool water must not exceed 75 mg/l. The stabiliser is contained in so-called "standard" chlorines, but does not dissolve in water.

When there is too much in the pool, the chlorine molecules' disinfecting power is slowed or even "blocked", which allows micro-organisms, such as algae, to proliferate, turning the water green:this is the phenomenon of over-stabilisation.

If we then add stabilised chlorine, instead of solving the problem we make it worse by further increasing the quantity of stabiliser.

Presence of green algae:

• Clean the swimming pool using a vacuum broom and tip the algae into the sewer system.
• Clean the filter and if you discover that it contains algae, treat the sand with hth®  FILTERWASH.
• Also brush the walls of the pool.
• Adjust the pH to between 7.0 and 7.4 with hth®  pH MINUS MICRO-BALLS.
• Use an anti-algae treatment that is preferably non-foaming like hth®  YELLOW SHOCK then perform a shock chlorination treatment with hth®  SHOCK^® Powder  before rinsing and washing the filter.

Over-stabilisation:

• Ask a pool specialist to check the stabiliser content. There must be less than 75 mg/l. 
• If this is not the case, partially or completely drain the pool depending on the amount measured.
• After refilling the pool to the correct level, adjust the pH level to between 7.0 and 7.4 with hth®  pH MINUS MICRO-BALLS.
• Then perform a shock chlorination treatment with hth®  SHOCK^® Powder that contains calcium hypochlorite (or unstabilised chlorine).
• To avoid a re-occurrence of this problem, we recommend regularly disinfecting your pool with hth®  STICK that contains unstabilised chlorine, also known as calcium hypochlorite (when there is no other product in the skimmers).

> To learn more about over-stabilisation: consult our specialist page.

   Did you know?

More than 60% of pool owners have problems with green water^*, and often state that this is the most difficult problem that they encounter during the high season.

^{* Result of a Uses and Attitudes survey conducted by Solenis in 2021}