How to Prevent Calcium Scaling on Pool Walls

Maintain calcium hardness levels between 200-400 ppm and use a scale preventer if necessary.

What Is Calcium Scaling?

Calcium scaling happens when there’s too much calcium in your pool water, especially when pH and alkalinity levels are too high. When the water becomes over-saturated, the excess calcium forms hard, crusty deposits on pool walls, ladders, and other surfaces.

There are two types of calcium scale:

• Calcium carbonate: This is the most common type. It’s white and flaky and can usually be removed with mild acid.
  

• Calcium silicate: This one is harder and forms grayish-white stains. It’s tougher to clean and usually requires stronger treatments.
  

If your pool surfaces feel rough to the touch or have white streaks, calcium scale is likely the culprit.

What Causes Calcium Scale?

There are a few main reasons why calcium scaling shows up in your pool:

1. High calcium hardness: If the calcium level is above 400 ppm, your pool is at risk for scale.
   

2. High pH or alkalinity: Imbalanced water chemistry causes calcium to come out of solution.
   

3. Heat: Warm water speeds up evaporation and scale buildup, especially in sunny or heated pools.
   

4. Hard tap water: If your local water supply has high mineral content, your fill water may be the problem.
   

How to Test for Calcium and pH

The first step in preventing calcium scale is to test your water regularly. Here’s what to look for:

• Calcium Hardness: Ideal range is 200–400 ppm
  

• pH Level: Ideal range is 7.2–7.6
  

• Total Alkalinity: Ideal range is 80–120 ppm
  
  

Use a reliable test kit or take a sample to your local pool store. If your levels are too high, you’ll need to take steps to lower them.

7 Tips to Prevent Calcium Scaling on Pool Walls

1. Maintain Proper Water Balance

Keeping your pH, alkalinity, and calcium hardness within the correct range is the most important step.

• Test water weekly
  

• Adjust pH with pH reducer if it goes above 7.6
  

• Use a calcium reducer or partial drain and refill if calcium is too high
  

2. Brush Pool Walls Weekly

Brushing helps prevent scale from forming by disrupting early deposits.

• Use a nylon brush for vinyl or fiberglass pools
  

• Use a stainless steel brush for concrete or plaster
  

• Focus on waterline and hard-to-reach areas
  

3. Use a Scale Inhibitor

Add a scale control product weekly or after every refill to stop calcium from sticking to pool surfaces.

• Look for sequestering agents made for calcium
  

• Follow the product directions carefully
  

4. Keep Your Pool Covered

Evaporation increases calcium concentration over time.

• Use a solar cover or pool blanket when not in use
  

• Helps reduce evaporation and water loss
  

• Also keeps debris out and reduces chemical use
  

5. Avoid Using Hard Water for Refills

If your tap water is high in calcium, consider using softened water or partial dilution.

• Use a hose filter when filling your pool
  

• Refill gradually to avoid chemical imbalances
  

6. Check Your Heater and Salt Cell

Calcium can build up inside your pool heater or saltwater generator, causing flakes to fall back into the pool.

• Inspect the heater’s heat exchanger for scaling
  

• Clean salt cell every few months to prevent calcium crust
  

7. Lower Water Temperature When Possible

Warmer water speeds up scale formation, especially if combined with high pH.

• Lower the thermostat on heated pools when not in use
  

• Avoid excessive heat during peak summer months
  

How to Remove Existing Calcium Scale

If you already see calcium buildup, here’s how to remove it safely:

Light Scaling

• Brush with a pool brush
  

• Use a mild pool surface cleaner or diluted vinegar
  

• Rinse well with pool water
  

Moderate Scaling

• Use a pumice stone on tile or plaster (never on vinyl)
  

• Apply a specialized scale remover
  

• Brush and rinse thoroughly
  

Heavy Scaling

• Lower water level slightly to expose affected area
  

• Use muriatic acid diluted with water (always wear gloves and eye protection)
  

• Apply with a sponge and scrub gently
  

• Rinse thoroughly with pool water
  

Important: Never use strong acids or harsh tools on vinyl liners or fiberglass surfaces. Always test on a small spot first.

Why Calcium Scale Is a Bigger Deal Than It Looks

Ignoring scale buildup can lead to long-term problems:

• It can stain and damage pool surfaces permanently
  

• It makes the water look cloudy
  

• It can clog pipes, filters, and heaters
  

• It creates a breeding ground for algae
  

Prevention is easier and cheaper than fixing severe scale damage. Regular water testing, brushing, and the right chemicals will save you time and money in the long run.

By staying on top of your water chemistry and cleaning routine, you can stop calcium scaling before it starts and keep your pool looking great all season long.