Calcium scale is one of the most unpleasant things you can get in your swimming pool. It is usually a white or grey stain that will form on the pool’s waterline, and it is often a result of having a pH or alkalinity imbalance.
The good news is that calcium scaling is quite an easy resolve if you know what to do. And with regular water testing and balancing, you can also ensure it will not have to deal with it often.
What is Calcium Scale?
Calcium scale is a chalky buildup that forms along a swimming pool’s waterline. This scaling will coat your pool vinyl liner, tile, or plaster finish and leave it looking dull, old, and unsightly.
Although the dull and old look is what many pool owners hate most about calcium scale, it also gives the surfaces a rough texture that can scratch swimmers. Also, the coarse calcium scale can tear your swimsuits, and it will make it uncomfortable to sit on the pool’s edges.
Besides forming along the waterline, the calcium scale can also build up on other pool fixtures such as filters and lead to clogging. Also, in some severe cases, the calcium scale will make your water cloudy.
There are two types of calcium scale: calcium carbonate and calcium silicate. Calcium carbonate is the most common type, and it is often a white and flakey buildup that remains behind when water evaporates.
Calcium silicate is white-grey, and it takes longer to build up, meaning by the time you notice it, the buildup will already be on other pool fixtures like pipes and filtration systems. Therefore, most calcium silicate cases will require you to call in a professional.
How Does Calcium Scale Buildup?
A buildup of calcium scale in swimming pools results from an increase in the water’s calcium hardness. The rise in calcium hardness occurs when the water pH and alkalinity levels rise.
Read more: How to Lower Alkalinity in Pools
As calcium hardness increases, some of the calcium in the water will start foaming and eventually harden around the waterline and pool fixtures, leaving behind a hard and rough scale. High pH levels will cause the calcium in the water to harden, and so the more calcium you have, the more the scaling.
However, calcium scaling can still occur even when the pool water has an optimal pH level. In such cases, the calcium scale remains behind as the pool water evaporates and often builds up along the waterline. This form of calcium scaling is more common for outdoor pools.
How to Remove Calcium Scale
When you notice calcium scale forming on your swimming pool, you need to dedicate enough time to deal with the problem and ensure you have the right product.
How you deal with the product depends on the pool finish but here is how to remove scale from tile and plaster finishes.
1. Removing Calcium Scale from Tile
Step 1: Lower the Water Levels
Before anything else, you will need to lower the water levels to expose the tiles with the calcium scaling. A garden hose will be handy here as it will make it easier to siphon off some water from your pool.
Step 2: Use White Vinegar and a Brush
Next, you should try scrubbing off the scaling from a few tiles using vinegar and a brush. Spray vinegar on the scale and give it around 20 to 30 minutes to set before scrubbing with a brush. If the scaling comes off, you should repeat the method for all other tiles.
Step 3: Use Acid Wash
If vinegar is not effective enough, try using an acid wash. Mix the acid wash with water in a large plastic bucket (use 1-part acid and 3-part water). You can then pour the acid wash in the areas with the scaling and give it a few minutes before scraping off the scales.
Step 4: Clean Filters and Keep the System Running
The last step is cleaning your filters to make sure there is no calcium scale there. Also, leave the filtration system running for a few hours to ensure you remove any loose calcium scale still in the water.
2. Removing Calcium Scale from Plaster
Step 1: Start with Pumice Stone
Start by reducing the water level to expose the calcium scale building up the waterline. Next, use a pumice stone to scrub off the scaling. If the problem is not very severe, the pumice stone should remove most of the scaling.
Step 2: Try an Acid Wash
If a pumice stone is not adequate, you should try an acid wash. You can quickly make one by mixing a good pool acid like the Certol International Acid Magic with water, following the provided directions.
An acid wash is effective at removing all kinds of calcium buildups. Plaster is hard to damage, so you can use a putty knife or wire-bristle brush when scraping off the scale. Also, make sure you rinse off the acid afterward.
Step 3: Run Filtration System
The last step is to run your filtration system to eliminate any scaling that might be floating in the water.
Tips to Prevent Calcium Scaling
- Keep monitoring your pH level and ensure you maintain it at the optimal range between 7.2 and 8.0.
- Brush and vacuum the swimming pool regularly to prevent the calcium from hardening on the waterline.
- Add a clarifier to the pool water regularly. Clarifiers will clump up the calcium together and make it easier to vacuum off the pool.
- Ensures you always cover your pool when not in use, as this will help minimize the rate of evaporation.
- Install a system that can remove calcium silicate and calcium carbonate from the pool water before building up. A reverse osmosis system can be handy here.
When the buildup is in its early stages, you can easily scrub it off. However, you will need to use an acid wash if the calcium is already hard.
It is always better to prevent the problem by monitoring the pool pH and calcium hardness and brushing the pool regularly.