How To Remove Black Spots From Underneath A Pool Liner

Sometimes black spots appear on the walls of your pool. This may be due to a local proliferation of algae, the presence of metal particles in the water or high humidity under the liner.

There are different types of stains, some are white and come from limestone, others are at the waterline and are caused by the sun and bathers. 
The black or green spots are caused either by algae that grow in the pool or by the presence of copper salts, iron or manganese in water, or by too much humidity under the liner.

A local proliferation of algae

Black or green spots often signify an algae invasion in your pool. The problem must be treated as quickly as possible to avoid the appearance of opaque green water.

  • Start by brushing the colored and slippery areas of your pool.
  • Then, you have to adjust the pH level of your pool, if necessary, to optimize the effects of the disinfectants. Using the following products: pH less liquid, pH more liquid, pH less powder, pH more powder.
  • It is important to ensure the proper functioning of your filter, to do a backwash to maximize its efficiency. Then turn it on to filter continuously. Using the following product: Filter and electrode descaler.
  • It is necessary to make a shock treatment using disinfectants such as chlorine or active oxygen. Using the following products: Shock catch, Chlorite, Chlorine shock tablets, Granuchlore 60, Granuchlore 90.
  • In addition, you must put a large dose of algaecide in the water. Using the following products: Algicide 100, Algicide 200, Algicide Multi.
  • Dead algae will cloud the water, so you have to use a flocculant to improve filtration and eliminate residues. Using the following products: Liquid flocculant, Flocculant in socks.

The Presence of Metal Iron’s In The Water

Black spots can also be caused by bacteria that produce hydrogen sulfide, which can migrate through membranes in liners.
In the presence of copper ions (which may come from the quality of the water or the treatment products used, such as certain algaecides or multifunctional chlorine) or iron and manganese, black spots (copper, iron, or manganese) appear. They frequently develop in the corners and hollow parts of swimming pools.
To fight against these stains, you must carry out a shock treatment with chlorine, combined with a sequestering product of metal irons.

Using the following products: Chlorine shock tablets, Granuchlore 60, Granuchlore 90, Chlorite, Metafloc.

Pink or Black Spots

Black, or sometimes pink, spots come from bacteria that have grown under your pool liner. They are due to too much humidity below it. To remove these black or pink spots, you must first lower the pH to 6, as well as the temperature. Using the following products: pH minus powder, pH minus liquid. Then, shock treatment with chlorine (about 10 mg / l). And end up filtering continuously for 48 hours. Using the following products: Shock catch, Chlorite, Chlorine shock tablets, Granuchlore 60, Granuchlore 90.

When black spots appear on the walls of your swimming pool, it is important for you to know the cause in order to carry out the appropriate treatment. In all the cases mentioned above, the problem must be quickly resolved to avoid the appearance of new spots.