This pool had large, sharp nodules growing from the pool’s finish. Read on to learn about pool finishes and their care, and how to remedy and avoid such issues.
We recently had a pool-owner call and ask us to take a look at their pool, it had formed sharp nodules and large deposits throughout the entire pool surface. The family could not use the pool without risking being cut!
Yes, we did help them with this issue, but why did it happen? Was anything wrong with the pool finish? The water? The chemistry?
Pool plaster
Concrete residential inground swimming pools generally have a plaster coating over the surface of the concrete pool shell. It takes a month for a concrete pool shell to cure. The pool shell will hold water, and it is best practice to apply a waterproofing agent to the pool shell before applying the finish.
Pool Plaster is protective and aesthetic. It protects the pool shell and provides beauty and personality to your pool. Pool plaster is made from a variety of natural materials such as rocks, pebbles, glass, and seashells. They give the pool color and sparkle and lend a smooth or raised texture to the pool. A binder made of polymers and coloring mix with the cement and the pebbles and other components, creating the beautiful and sturdy finish.
Application
Pool plaster application requires highly trained and certified technicians. Watching a crew apply the finish is an amazing display of teamwork and expertise. The plaster and its components arrive in bags and are mixed with water onsite. This gives the plaster finish a natural appearance. Pool plaster has subtle variation, as in nature.
The plaster is applied to the pool shell and then hand troweled. The workers wear special boots with cleats to avoid leaving footprints in your pool. The temperature and the weather must be just right for quality application.
Curing the plaster
When the pool finish is all in place, it sets for a short time, and then it is etched to reveal the pebbles and other components in the finish. Next it is time to fill the pool. Pool plaster cures to its hardened state under water. The properties of the fill water are very important to the proper curing and longevity of the finish. A new pool’s finish is finicky until it cures. At Agile Aquatic, we use the Orenda startup for new plaster.
We test the source water and mix with appropriate pool chemicals to ensure that the fill water is balanced. The Orenda products we prefer are non-toxic and keep pool water chemicals in solution—as opposed to them falling out of the water and collecting on the bottom of the pool, staining the new plaster.
Filling the pool with balanced water and starting the circulation system once the pool is partly filled helps the plaster to cure properly. It is important to fill the pool continually; any stoppage can cause a permanent “bathtub ring” around the pool/spa.
Once the pool is filled, it is important to brush the pool daily for the first 1-2 weeks. Brushing disrupts any organic biofilm from taking hold and removes plaster dust to the circulation system, where it can be filtered out of the pool.
So, what happened?
Back to our pool in question: Why were there nodules growing in their pool? It turns out that the company that built the pool had a malfunction with the pool cover. The cover remained closed for quite some time—weeks—after the pool was filled. The pool had been filled with untreated, unbalanced well water. The pool was not brushed. Plaster dust, metals and contaminants in the water were allowed to adhere to the pool and spa bottom.
The source well water at this location is quite high in alkalinity, which is corrosive over time. Calcium is another chemical that is very important to pool water balance. Water seeks calcium. If the pool water does not have an adequate level of calcium, it will pull calcium from the nearest source—the pool finish.
The combination of plaster dust and precipitates with corrosive water and low calcium, and lack of brushing, plus a closed cover, caused conditions that allowed the nodules to form.
Agile Aquatic recommends using a tent to contain debris when sanding/polishing an indoor pool. This keeps the fine particles from harming surfaces inside the home.
The solution
Once our testing and analysis were complete, we consulted with our pool finish expert. We decided that the finish could be salvaged—the best course of action was to polish the nodules, sanding down a layer of the finish.
For extra assurance, two coats of Microglass were applied to the polished finish. Microglass absorbs into the microscopic pores of the pool finish, protecting it and allowing it to breathe. This coating greatly cuts down on plaster dust, and extends the life of your pool finish..
We started the pool with an Orenda startup to give the refurbished finish the best start possible. The homeowners were provided with an operation manual, instructions in pool care, and training on how to use the app to calculate chemical doses.
So far so good! We are so glad to be able to restore the enjoyment of their beautiful pool to this family!
Do you want to improve the look and longevity of your pool’s finish? Give Agile Aquatic a call, 319-361-7940!