Green pool water
If, like over 60% of pool owners, you are experiencing green water issues*, do not panic!
HTH will help you get rid of unsightly algae and restore crystal clear water.
Possible causes:
The green colouring of swimming pool water is generally caused by the presence of algae, whose growth is encouraged or even accelerated by:
- Insufficient or defective filtration (➽ calculate your ideal filtration time)
- Chlorine level too low and/or pH too high
- High water temperatures promote photosynthesis.
- Over-stabilisation of the water
The stabiliser is contained in what are known as ‘classic’ or ‘stabilised’ chlorines. Its role is to protect the chlorine from sunlight (UV rays), which reduce its lifespan and effectiveness.
The only problem is that the stabiliser does not dissolve in water and does not evaporate either.
The stabiliser level in the water must not exceed 75 mg/l.
When there is an excessive amount in the pool, the disinfecting action of the chlorine molecules is slowed down or even ‘blocked’, allowing micro-organisms such as algae to proliferate, turning the water green and causing it to ‘turn’: this is the phenomenon of over-stabilisation.
Introducing stabilised chlorine at this stage will aggravate the issue rather than resolve it, as it will further raise the stabiliser concentration.
What to do if your pool water is green?
➽ Treatment advice:
1. Treating green algae:
In all cases, the first step is to thoroughly clean the pool and the filter.
- Clean the pool using a vacuum cleaner with algae removal into the drain.
- Clean the filter and, if you detect algae in the filter, treat the sand with HTH FILTERWASH.
- Brush the pool walls as well.
- Adjust the pH between 7.0 and 7.4 using HTH pH MINUS micro-balls to lower the pH or if you need to raise it, using HTH pH PLUS powder.
The ideal pH is between 7.0 and 7.4.
7.4 is also the pH of tears, blood and mucous membranes in the human body.
2. Over-stabilisation:
If, despite your efforts, the water remains green and the algae do not disappear, it means that the pool water is over-stabilised, as explained above.
- Have the stabiliser content checked by a pool specialist. This value must be less than 75 mg/l.
- If this is not the case, partially or completely empty the pool depending on the value obtained.
- After refilling the swimming pool, adjust the pH between 7.0 and 7.4 using HTH pH MINUS micro-balls to lower the pH or if you need to raise it, using HTH pH PLUS powder.
- Then perform shock chlorination with HTH SHOCK powder based on calcium hypochlorite at a rate of 150 g per 10m³ of water (unstabilised chlorine).
with handle and dosing cap
➽ Carry out a regular and effective disinfection:
To prevent this from happening again, we recommend that you treat your pool regularly with HTH STICK which is based on unstabilised chlorine, also known as calcium hypochlorite (make sure there are no other products in the skimmers beforehand).
1 stick for 20 m³
every 5 days
- Do not mix calcium hypochlorite with any other treatment product.
- Never dissolve before use.
- Use biocidal products with caution.
- Before use, read the label and product information.
* Results of a Usage and Attitudes study conducted by Solenis in 2021
