Calcium Nodules

Calcium Nodules In Pool - How To Get Rid Of Them?

Calcium nodules in a pool are small, unsightly bumps that can form on plaster, fibreglass, or tile pool linings. These nodules form when elements in your pool’s lining interact with the chemistry of your pool’s water, and tend to be a cause for concern about the integrity of your pool’s surface.

In this article, we will talk about what calcium nodules are, what causes them to form, and removing calcium nodules in your pool.

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What Are Calcium Nodules In A Pool?

Calcium nodules in a pool are small formations composed of calcium carbonate. These nodules have an unsightly appearance that can look like excess caulking, and they are most often found in plaster pools.

Calcium nodules can also occur in fibreglass pools and in the grout lines of tile pool linings.

Calcium nodules should not be mistaken for various presentations of scale. Unlike scale, nodules are very three-dimensional in appearance and are always significantly raised from the surface, almost as if these solid bumps are ‘gushing out’ of the pool’s lining.

They are typically somewhat smooth and bumpy in texture, and may feel somewhat like chalk.

What Causes Calcium Nodules?

Calcium nodules are typically the result of a poor plastering job, but can also be a sign of normal ageing in older plaster pools. When air bubbles become trapped in dried plaster, this leads to delamination of the pool lining, allowing elements of it to become exposed to the pool water.

When the calcium hydroxide in these various types of pool linings gets exposed to pool water, it combines with alkaline elements in your water to form the unsightly calcium nodules that you see.

It is a common myth that calcium nodules are caused by issues with pool chemistry alone. Chemically imbalanced pool water by itself is not enough to cause the formation of calcium nodules.

If your pool is structurally sound, the pool’s water will not come in contact with the calcium hydroxide in the pool lining that causes these nodules to form.

How To Remove Calcium Nodules From Your Pool

It is possible to remove calcium nodules from your pool by scraping them off with a stiff trowel, but because these formations are caused by structural issues with your pool’s lining, they will simply reform over time.

We recommend using caution if you intend to scrape calcium nodules from your pool, as this action could further damage the lining of your pool, and successful removal may even allow more water into the delaminated areas.

The only true fix for calcium nodules in your pool is to get your pool’s lining redone. Plaster pools will need to be entirely replastered, and for best results, this should be done by a team of professionals with a history of quality craftsmanship.

Fibreglass pools experiencing calcium nodules are experiencing delamination issues with the gel coating of the pool, and may also be developing problems deeper within the lining.

Calcium nodules in this type of lining should be evaluated by fibreglass pool specialists, as this lining type is unique.

In cases where calcium nodules are forming in a tile pool, you may be able to perform a small, DIY repair of the affected area, provided that these nodules are only occurring in one small area of your pool.

If you are not comfortable with at-home fixes, have a more severe issue with calcium nodules, or would just appreciate having the guarantee of more long-lasting results, it’s always a good idea to get in touch with professionals who service pool linings.


Calcium nodules form in a pool when elements of the pool’s lining are exposed to pool water through damage, wear, or delamination.

These nodules can be removed by scraping, but this is only a temporary fix as the nodules will reform. The only way to truly fix calcium nodules is to get the lining of your pool repaired or replaced.

Do you have any questions about removing calcium nodules in your pool, or how they form in the first place? Get in touch with us in the comment section, we’d love to help!

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.