Water with high levels of dissolved minerals, such as calcium and magnesium, can show up throughout your home as soap scum in your tub, chalky deposits on your shower head, and scale buildup that impacts the performance of your appliances. Unfortunately, it can also affect your swimming pool. This guide will show you how to treat hard water in your pool before it tanks your water quality and damages your equipment.
What does hard water do to a pool?
Before we explore how to treat hard water, it’s important to understand the effects of heavy mineral loads. Here are some of the signs and symptoms of hard water in your pool, spa, or hot tub:
Creates scale buildup
Hard, white mineral deposits on your pool walls, tile lines, ladders, and other surfaces are a classic sign of hard water. However, these visible effects may indicate unseen stains in your pump and filtration system, which may increase internal pressure, reduce water flow, and make your pool much harder to clean.
No matter the location, hardened calcium carbonate deposits often require professional treatment.
Damages heaters and salt cells
When scale accumulates inside a pool heater, heat exchanger, or salt chlorine generator, it acts as an insulator, causing these machines to work harder and less efficiently. Your equipment may use more power than usual, require more frequent maintenance, and fail prematurely.
Clouds the water
Particularly high calcium levels and imbalanced water chemistry can cause minerals to come out of solution and give your pool water a milky, cloudy appearance.
What causes hard water in a swimming pool?
Let’s assess the underlying causes of hard water in a swimming pool so you can determine how to effectively treat it.
Your source water
Among all possible causes, the water you use to fill your pool has the biggest impact on calcium hardness. Tap and well water often contain elevated levels of dissolved minerals, so it’s possible your water source is the primary culprit behind the issue.
You might feel tempted to install a water softener to remove calcium and magnesium before it enters your home, but this isn’t recommended. Remember, your pool needs a certain amount of dissolved minerals to protect your pool from corrosion, wear, and calcium leaching.
Evaporation and top-offs
The natural evaporation process reduces the water level in your pool, leaving behind dissolved minerals. In turn, those particles become more concentrated as water levels drop. Unfortunately, if your water source is also hard, refilling your pool will add more calcium and magnesium, so top-offs ultimately increase the pool's hardness.
Pool chemicals
Certain chemicals, such as calcium hypochlorite, are used to shock pool water without raising levels of CYA and other conditioners. However, not all homeowners understand how they affect calcium hardness. This is why it’s so important to keep a testing kit handy and regularly assess your water chemistry.
Imbalanced pH and alkalinity
While high pH and total alkalinity levels alone don’t increase calcium hardness, they can raise the risk of dissolved calcium solidifying and forming scale on pool surfaces. Under these conditions, mineral deposits can develop quickly, becoming out of control at a rapid pace.
How to treat hard water in your swimming pool
No one wants to swim in a cloudy pool that irritates their skin and dries out their hair, so let’s discuss how to treat hard water
1. Test your water
Always test your pool’s water chemistry to determine the precise concentration of dissolved minerals. Be sure to use the right type of test kit. For example, you should use a saltwater testing kit for a saltwater pool. The results will reveal how hard or soft your water is and help determine the best treatment plan.
The ideal range is between 100 and 400 ppm.
2. Drain and refill
If your readings show extremely high calcium hardness levels, starting from scratch may be your best option. Consider partially draining the pool, then refilling it with water that’s lower in dissolved solids. Although some instances require complete draining, these are rare and time-consuming, so it’s best to start conservatively.
On the other hand, many people choose to hire a service to perform reverse osmosis on their existing water with a specialized machine.
3. Use a scale preventer
Softening your water may not be the best idea, but a scale preventer can help you work with higher calcium hardness levels. Scale inhibitors or sequestrants don’t actually remove calcium from the water, but they keep the particles dissolved, so they can’t form scale deposits.
4. Switch sanitizers
Pools that require frequent applications of calcium hypochlorite are at risk of elevated hardness. Consider using liquid chlorine or a salt chlorine generator as an alternative solution.
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