What is Osmosis?

What is Osmosis?

Osmosis, also known as black plague, refers to bumps or blisters that appear on a pool’s surface based on a failed watertight seal.

These imperfections exist permanently, or may come and go over time. The bumps that arise are often one to four inches in diameter, feel hard or porous to the touch, and may not pop or crack when stepped on or pressed. Some may leak a brown or black tar-like substance, causing alarm in pool owners concerned with possible safety consequences. Treatments like staining or popping will not diminish the effects, and shocking with high doses of chlorine can only exacerbate the problem.

Why does Osmosis Occur?

Osmosis occurs when air and water escape through a pool’s lining.  Generally these issues can arise in any number of ways, but are generally related to the installation and care of a pool.

What do Osmotic Blisters Look Like?

They are normally the size of a 20 cent piece or smaller and look just like you would expect a blister to look…like slight bubbles that are raised on the surface of the pool, they can also appear like black spots.  They do not go away and unfortunately there’s no quick fix either. 

How can Osmosis be Repaired?

As stated above there is no quick fix, unfortunately the existing interior needs to be grinded back to expose all of the Osmosis.  The Osmosis is then removed and a filling agent is applied that is suitable for fibreglass pools.  New fibreglass matting is then installed and fill coat and final top coat are applied.

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