How Do I Prevent Metal Staining in My Hot Tub?

Use a spa metal control chemical to bind metals in the water and prevent staining. Regularly test the water if your source has high metal content, and consider using a pre-filter when filling the tub.

Why does metal staining happen in hot tubs?

Metals like iron and copper in water oxidize and stick to surfaces, creating stains. High sanitizer levels or pH imbalances make it worse.

What Causes Metal Staining in Hot Tubs?

Metals in Source Water

Water from wells or old pipes often contains metals such as copper, iron, and manganese. When added to the hot tub, these metals may oxidize.

Signs of metal contamination:

• Rust-colored, green, or blue stains

• Cloudy water that clears when still

• Metallic smell

High Sanitizer Levels

Chlorine and bromine oxidize metals, which can cause them to precipitate and settle on hot tub surfaces.

Effects of high sanitizer:

• Speckled or blotchy stains

• Rough texture on shell

• Discoloration near jets or drains

pH and Alkalinity Imbalance

When pH is too high or too low, metals become unstable in the water and attach to surfaces.

Problems caused by imbalance:

• Stains forming quickly after shocking

• Surfaces feeling gritty

• Increased difficulty removing stains

Steps to Prevent Metal Stains

1. Test Your Water for Metals

Before filling your hot tub, test the water for metals using a test kit or have it professionally tested.

• Detects copper, iron, and manganese

• Helps you plan your maintenance strategy

2. Use a Metal Sequestrant

A metal sequestrant binds metal particles and keeps them suspended so the filter can remove them.

• Add when filling or topping up water

• Reapply weekly or after adding fresh water

• Follow manufacturer’s dosage instructions

3. Keep Water Balanced

Maintaining proper pH and alkalinity reduces metal reactivity.

Ideal levels:

• pH: 7.4 to 7.6

• Alkalinity: 80 to 120 ppm

Test at least twice a week and adjust as needed.

4. Avoid Over-Shocking

Using too much shock can oxidize metals and cause staining.

• Use the recommended dose of shock

• Shock at night to minimize UV impact

• Run pump and jets to circulate water evenly

5. Clean and Replace Filters Regularly

Filters trap suspended metal particles. Keeping them clean prevents metals from settling.

• Rinse filters weekly

• Deep clean monthly

• Replace annually

6. Use a Pre-Filter When Filling

Attaching a hose pre-filter removes metals before they enter the hot tub.

• Affordable and easy to use

• Especially helpful if you use well water

How to Treat Existing Metal Stains

Lower pH Slightly

If stains have already formed, lowering the pH can help dissolve them back into the water.

• Adjust pH to around 7.2 temporarily

• Brush affected areas gently

Add More Sequestrant

Increasing the amount of sequestrant can help lift stains from surfaces.

• Follow shock and sequestrant treatment instructions

• Circulate water for several hours

Professional Cleaning

For stubborn stains, you may need a professional service or a specialized stain remover.

• Always test cleaners in a small area first

• Avoid abrasive scrubbing, which can damage surfaces

Long-Term Maintenance Tips

Establish a Routine

Consistency prevents metals from building up.

Suggested routine:

• Weekly: Test water, add sequestrant, rinse filters

• Monthly: Deep clean filters, inspect for stains

• Quarterly: Drain, clean, and refill spa

Keep the Cover On

When not in use, keep your hot tub covered to prevent debris and dust, which can contain metals, from entering the water.

Monitor Source Water Changes

If your water source changes, test it again for metal content to adjust your treatment accordingly.

When to Call a Professional

If stains persist despite your efforts, it may be time to seek expert help.

Call a Technician If:

• Stains return quickly after cleaning

• Water remains cloudy and metallic smelling

• Equipment shows signs of corrosion

A professional can test your water more thoroughly and recommend advanced solutions.

Enjoy a Spotless, Stain-Free Hot Tub

Preventing metal stains takes a little planning and consistent care. By testing your water, using a sequestrant, and maintaining proper balance, you can keep your spa surfaces looking clean and inviting for every soak.