Pool Stains 101: What You Need to Know
If you own a pool, you know that stains can be a frustrating and inevitable part of the experience.
Let’s break down the types of stains you might encounter—organic, metal, and calcium scale—so you can minimize this annoying blemish.
Organic Stains
Where They Come From
- Leaves and Vegetation: Those pesky decaying leaves and other plant debris can leave behind unsightly brown or green stains as they break down and release tannins into the water.
- Algae: If your pool’s not getting enough attention, algae can start to bloom, turning the water green and leaving behind stains on the walls and floor.
- Sunblock and Oils: Enjoying a sunny day? Sometimes your sunblock, lotions, and oils can leave behind yellow or brown stains, especially on white plaster.
How to Prevent Them
- Regular Cleaning: Make it a habit to skim the pool daily and vacuum weekly. This will help remove organic materials before they break down and stain. Keeping your skimmer baskets clear means they keep working, pulling leaves into the baskets before they can sink to the floor.
- Keep It Sanitized: Maintaining appropriate chlorine levels is crucial for preventing algae growth and keeping your pool water clear and inviting.
- Good Water Circulation: Ensure your pool’s water is circulating properly. Good circulation helps prevent debris from settling and promotes even distribution of chemicals.
What to Do If You See Them
- Enzyme Cleaners: These special cleaners break down organic matter, helping to keep your pool fresh and reducing stains.
- Shock Treatments: Chlorine can break down tannins- dry Calcium Hypochlorite along with aggressive brushing can usually reduce or eliminate these types of stains
Metal Stains
Where They Come From
- Iron: This often sneaks in from well water or corroded metal parts in your pool system, causing reddish or brown stains that can be quite noticeable. Iron can also bleed through from the steel rods inside the pool shell.
- Copper: Copper can enter the pool from old equipment, plumbing, or certain algaecides, leading to eye-catching green or blue stains on pool surfaces. High copper levels can also react with chlorine to create black stains as a chemical reaction.
- Manganese: This mineral can create dark brown or black stains, commonly associated with high mineral content in water, especially from well sources.
- Nickel and Silver: If you have nickel-plated components or high concentrations of silver in your water, you might spot greenish or gray stains appearing over time.
How to Prevent Them
- Use a Sequestrant: Regularly adding a sequestrant can help keep metals in solution, preventing them from settling and causing stains.
- Skip the Well Water: If you are on a well, fill your pool with water trucked in from public treated water, which typically has lower levels of metals and minerals, reducing the risk of staining.
- Balance Your Chemistry: Keeping your water within the Langelier Saturation Index (LSI) range not only helps prevent stains but also minimizes corrosion of your pool surfaces and equipment.
What to Do If You See Them
- Test Your Water: Regular testing is essential for detecting metal levels. Adjust your water chemistry as needed to keep those stains at bay.
- Stain Removers: There are specialized stain removal products designed specifically to tackle metal stains effectively without damaging your pool. These are difficult to administer, and not always reliably effective, but in small areas can be a realistic option.
- Metal Eliminators- These pods or “power paks” pull in metals to eliminate them from your pool water, or at least reduce them. They are temporary and must be replaced periodically.
Calcium Scale
Where It Comes From
- High Calcium Saturation: If your pool water is too hard, it can lead to the formation of scale, which manifests as rough, white deposits on surfaces. Although, this does not just come from having high calcium, which is only one factor. Calcium scaling is a product of the combination of many factors. To determine if your pool water is scale forming use an LSI calculator. Here is one that is easy to use: https://www.orendatech.com/pool-dosing-calculator
- Every pool has some amount of calcium scale. It is least noticeable on white plaster, because calcium is white! If you have a darker quartz or pebble surface you will notice this much more as it causes a cloudy white look.
How to Prevent It
- Check and adjust water chemistry every week: Adjust chemistry to stay as close to LSI zero as possible.
- Sequestrants- these scale control products can reduce existing scale, although very slowly, and with perfect water conditions.
- Brush It Off: Make it a routine to brush your pool surfaces regularly. This can help dislodge early-stage scale before it becomes a bigger problem.
What to Do If You See It
- Calcium scale can be reduced slowly with combination of sequestrants, lower range LSI water chemistry, and aggressive brushing.
- Acid Wash or Acid Bath: For heavy scale buildup, an acid bath (water stays in) or acid wash (pool must be drained) can sometimes remove stubborn deposits, restoring the look of your pool surfaces. These cleaning methods are aggressive and very harsh on your surface, and should only be used in certain circumstances.
- Calcium scale is present in every plaster pool at some level. It is more visible in darker colored surfaces, because calcium is white.
Water Chemistry is KEY! We hear from our clients all the time:
“But my well water is treated!”
That’s great! And means it’s safe to drink. That does not mean you have removed all of the metal content from groundwater that causes pool staining. Even treated well water is quite different from public water.
“All I have ever done is add chlorine to the pool and my water stays clear. Why should I do extra work?”
Keeping your water clear is different from protecting pool plaster. Clear water can be aggressive, cause staining, or form scale.
I have never monitored or adjusted my water chemistry in the winter before. Is that really necessary?
Temperature greatly affects calcium saturation water. During the off season water temperatures drop from 65 to 35 (or even 32), and then rise to around 65 again as pools open in the spring. During that time pools with mesh covers also have several feet of dilution due to rain. These changes should be accounted for in order to protect pool plaster.
While stains are a common part of pool ownership, knowing what to look for and how to handle them can make all the difference. With regular maintenance, a few smart products, and balanced water chemistry, you can reduce the incidence and severity of stains. It’s also important to have realistic expectations about what is normal and inevitable in such a sensitive surface in an outdoor environment.