Why Your Pool Has Stains and How to Fix Them

Are you wondering why your pool has unsightly stains and how to fix them? Pool stains can develop for various reasons, from imbalanced water chemistry to the presence of metals, minerals, or organic debris.

These stains can range in color and texture, making your pool less visually appealing and more challenging to maintain.

We will be going over:

• What causes pool stains and how to prevent them.
• How to remove stubborn stains using sequestering agents and specialized products.
• Tips for long-term maintenance to keep your pool stain-free.

Stain Prevention with Sequestering Agents

Swimming pools are susceptible to developing various stains on their surfaces over time. These stains can arise from multiple sources, including poor water chemistry, heavy metals, minerals, or accumulated debris such as leaves and dirt that find their way into the pool water.

To mitigate the most common cause of pool surface staining, it is crucial to maintain proper water balance consistently and keep the pool clean throughout the year.

However, even with meticulous chemical balance and excellent maintenance practices, pools can still develop stains from metals or minerals. These stains often appear in light brown or turquoise hues.

Using a sequestering agent and maintaining a balanced pH is essential to prevent such stains. A sequestering agent can be added to the pool as frequently as monthly to prevent stains, although most pools will only require this product once or twice a year to achieve effective stain prevention.

A sequestering agent works by binding the minerals or metals in the water, preventing them from precipitating and adhering to the pool surface. It also inhibits calcium from depositing onto the pool walls and tiles, provided the pH levels remain balanced.

This proactive measure helps keep the pool walls and tiles looking new for longer.

Addressing Calcium Buildup

Regular use of a sequestering agent, consistent pH monitoring, and prompt debris removal are essential components of an effective stain prevention strategy. Taking these proactive steps ensures that your swimming pool remains a beautiful, inviting oasis for years.

Calcium buildup in swimming pools is a common issue that requires special attention. If a pool consistently maintains a high pH level, especially when it is newly constructed or has just been resurfaced, calcium can accumulate on the surface and tiles.

This buildup often appears as a discoloration that differs from the pool’s original surface, particularly noticeable in pools with colored plaster like Tahoe blue. These “stains” are typically light grey or white and result in a slightly rough texture when you run your hand over the walls or tiles.

Contrary to common belief, these are not true stains but a chemical reaction due to poor maintenance practices. At this stage, professional intervention is often necessary. Experts must drain the pool and either acid wash or sand the calcium deposits from the surfaces.

This process can be expensive and should ideally be avoided by conducting a chemical startup on all newly resurfaced or recently filled pools. Regular pool maintenance, including weekly pH balancing, is crucial to prevent such issues. Maintaining a pH between 7.4 and 7.6 will effectively stop calcium buildup on the pool surface.

A sequestering agent can also help avoid stains and scale, although it will not remove the existing calcium scale.

Effective Stain Removal Techniques

Several methods can be employed to remove stains from your pool, depending on the type and severity of the stain.

Ascorbic Acid: The Natural Stain Remover

Ascorbic acid, commonly known as Vitamin C in powder form, is an effective stain remover for certain types of stains, particularly those caused by copper (turquoise) or silver (grey).

Before purchasing a commercial product, you can test the efficacy of ascorbic acid by using a chewable Vitamin C tablet. Rub the tablet on the stained area for several minutes. If the stain fades, you can use ascorbic acid in powder form, available at pool stores.

Two pounds of ascorbic acid typically treats about 20,000 gallons of water. Carefully add the powder to the pool; it is lightweight and can easily blow away. After an hour, run the pump and brush the entire pool. While you may see immediate results, the stains will diminish over the next few days.

One downside of ascorbic acid is that it removes all chlorine from the pool. You must wait a week before gradually raising the chlorine levels back to normal. Doing this too quickly can cause the metals that caused the stains to redeposit onto the pool walls and increase the risk of green algae due to the lack of chlorine. It is best to use this product in the spring when the sun is less intense and the water is more forgiving regarding algae growth.

When shocking the pool, dilute the liquid chlorine in a bucket of water before adding it to the pool. Gradually add small amounts of chlorine and use a floating chlorinator with tabs to gently raise the chlorine level back to normal.

Oxalic Acid: Removing Brown Stains

Oxalic acid is another effective stain remover for brown stains caused by iron or organic material. This heavy powder should be diluted in a bucket of water before being added directly to the pool while the pump runs. Oxalic acid works slowly over a few days, but swimming can resume about six hours after application.

To enhance the effectiveness of oxalic acid, you can lower the pool’s pH to 7.0 – 7.2 using muriatic acid. Depending on the pool’s size and the current pH level, you may need a quarter to an entire gallon of acid.

Most average-sized plaster pools can safely receive half a gallon of muriatic acid if the pH is within the normal range before adding the oxalic acid. Wait three days for the product to work before raising the pH to average.

Alternative Stain Removal Methods

In some instances, professional services may be required to remove stubborn stains. Pool companies can drain and lightly acid wash the pool walls, though this process will slightly erode the pool’s surface by removing a layer of plaster. For newer pool surfaces, the aesthetic improvement often outweighs the minor surface damage.

Stains caused by excessive copper in the water, such as turquoise stains, can be particularly challenging to remove with standard products. In such cases, a drain and light acid wash might be necessary to eliminate most stains. However, the most effective way to remove copper sulfate stains is to resurface the pool often.

To prevent future copper stains, avoid using too much copper algaecide and check the copper content in your pool fill water.

If your fill water contains high levels of metals, consider using a sequestering agent from the start to prevent stains. Your water company can provide test results to help you identify if your fill water is the culprit.

Preventive Measures for a Stain-Free Pool

After successfully removing existing stains, implementing preventive measures is crucial to maintaining your pool’s pristine condition.

Regular use of a sequestering agent, consistent pH monitoring, and prompt debris removal are essential components of an effective stain prevention strategy. Taking these proactive steps ensures that your swimming pool remains a beautiful, inviting oasis for years.