The Treatment Of Your Spa

Introduction

A spa is meant to be a sanctuary of relaxation and wellness. However, maintaining clean, balanced, and safe spa water is essential for enjoying these benefits. Without proper water treatment, your spa becomes a breeding ground for bacteria, algae, viruses, and other harmful microorganisms—turning your wellness investment into a health hazard.

The good news: spa water treatment is straightforward once you understand the basics. This comprehensive guide covers everything you need to know about maintaining pristine spa water: why treatment is essential, which products to use, how to test water quality, and how to establish a maintenance routine that keeps your spa safe and inviting year-round.

Why Treat Spa Water? Understanding the Importance

Spa water treatment isn’t optional—it’s essential. Here’s why proper treatment matters.

The Health Risks of Untreated Spa Water

When spa water is left untreated, dangerous organisms thrive:

Bacteria:

• Legionella pneumophila (causes Legionnaires’ disease—severe pneumonia)

• Pseudomonas aeruginosa (causes hot tub folliculitis and ear infections)

• E. coli and other pathogenic bacteria

• Staphylococcus aureus (causes skin infections)

Viruses:

• Norovirus (highly contagious gastrointestinal illness)

• Hepatitis A

• Adenovirus (causes respiratory infections)

Fungi:

• Candida species (causes yeast infections)

• Dermatophytes (causes athlete’s foot and ringworm)

Algae:

• Green algae (clouds water, provides breeding ground for bacteria)

• Black algae (very difficult to eliminate once established)

Parasites:

• Cryptosporidium (causes severe diarrhea, resistant to chlorine)

Why Spa Water is Particularly Vulnerable

Spas are particularly vulnerable to contamination because:

• Hot water accelerates bacterial growth: Bacteria thrive at warm temperatures (77–104°F is ideal for many pathogens)

• High bather load: Multiple people introduce contaminants simultaneously

• Bather hygiene variations: Not everyone showers before entering

• Body fluids and oils: Sweat, urine, cosmetics, sunscreen all contaminate water

• Small water volume: Unlike pools, spas have limited water to dilute contaminants

• Intense water circulation: Contaminants are rapidly distributed throughout spa

What Proper Treatment Accomplishes

Regular spa water treatment:

• Kills harmful microorganisms (bacteria, viruses, fungi, parasites)

• Prevents algae growth (maintains water clarity)

• Maintains chemical balance (pH, alkalinity, sanitizer levels)

• Reduces odors and irritation (properly balanced water doesn’t smell or burn eyes/skin)

• Extends equipment life (balanced water prevents corrosion and scaling)

• Protects bather health (prevents infections and illnesses)

• Maintains water clarity (pleasant aesthetic experience)

The Four Pillars of Spa Water Treatment

Proper spa water treatment involves four essential components working together:

1. Filtration: The Foundation

Mechanical filtration removes:

• Dirt and debris

• Dead skin cells

• Hair and fibers

• Algae particles

• Other suspended solids

Filtration system components:

• Pump (circulates water through filter)

• Filter media (cartridge, sand, or diatomaceous earth)

• Skimmer basket (removes surface debris)

Filtration frequency:

• Run filter 4–8 hours daily minimum

• Run longer in heavy use (24 hours ideal for some systems)

• Clean cartridge every 2 weeks or when pressure gauge indicates

• Replace cartridge every 12–18 months

Without proper filtration:

• Chemical treatment becomes ineffective (debris blocks chemicals from reaching water)

• Water becomes cloudy

• Equipment wears faster

• Chemicals need frequent replenishment

2. Sanitization: Killing Microorganisms

Sanitizers destroy harmful microorganisms. Common sanitizers include:

• Chlorine

• Bromine

• Active oxygen

• PHMB

• Ozone

(Details below)

3. pH and Alkalinity Balance: Optimizing Treatment Effectiveness

pH (acidity/alkalinity):

• Ideal range: 7.2–7.8

• Too low (below 7.2): Corrosive, irritating, chlorine ineffective

• Too high (above 7.8): Scaling, cloudy water, chlorine ineffective

Alkalinity (buffer system):

• Ideal range: 80–120 ppm

• Too low: pH swings (unstable)

• Too high: Scaling, cloudy water

Why balance matters:

• Sanitizers work optimally only at correct pH

• Unbalanced water causes scale buildup (on equipment, spa surfaces)

• Unbalanced water irritates skin, eyes, mucous membranes

• Unbalanced water corrodes equipment

4. Regular Testing: Monitoring System

Test spa water regularly:

• Weekly minimum for used spas

• Twice weekly for frequently used spas

• Daily if experiencing issues

What to test:

• Sanitizer level (chlorine, bromine, etc.)

• pH

• Alkalinity

• Calcium hardness (if applicable)

Spa Treatment Product Options: Detailed Comparison

Different sanitizers have different advantages and disadvantages. Choose based on your priorities, budget, and spa type.

Chlorine: The Traditional Standard

How it works:
Chlorine kills microorganisms by breaking down their cell walls and disrupting their metabolism.

Forms available:

• Tablets (trichlor): Easy to use, placed in skimmer or floating dispenser

• Powder (calcium hypochlorite): Fast-acting, dissolves quickly

• Liquid (sodium hypochlorite): Immediate action, good for shock treatment

Advantages:

• Most affordable: ~$20 per 5 kg of tablets

• Widely available: Easy to find at any pool/spa supplier

• Effective: Kills all types of microorganisms, algae, and viruses

• Proven track record: Decades of reliable use

• Fast-acting: Quickly eliminates contaminants

• Measurable: Easy to test chlorine levels

Disadvantages:

• Temperature sensitive: Loses effectiveness in hot water

• pH sensitive: Effectiveness reduced if pH is high

• Chemical smell: Strong chlorine odor (indicates chlorine gas release)

• Skin/eye irritation: Can irritate sensitive individuals

• Incompatible with some spas: Damages inflatable spa materials

• Stabilizer required: Stabilized chlorine (dichlor) recommended for spas

Best for:

• Budget-conscious spa owners

• Smaller spas with moderate use

• Those prioritizing affordability

Cost: ~$20 per 5 kg of tablets; typically need 1–2 tablets every 1–2 days depending on usage

Compatibility:

• Can be combined with active oxygen for shock treatment

• Cannot be combined with bromine

• Cannot be combined with PHMB

Bromine: The Premium Alternative

How it works:
Bromine kills microorganisms similarly to chlorine but remains effective across a wider range of conditions.

Forms available:

• Tablets: Most common form

• Powder: Less common for spas

Advantages:

• Temperature stable: Remains effective in hot water (65–104°F range)

• pH stable: Works well across pH range (6.8–8.0)

• UV stable: Not affected by sunlight

• No irritating odor: Doesn’t produce strong chlorine smell

• Gentle on skin/eyes: Less irritating than chlorine

• Gentler on equipment: Reduces corrosion

• Longer-lasting: More stable, requires fewer additions

• Effective against algae: Kills all microorganism types

Disadvantages:

• More expensive: ~$65 per 5 kg of tablets (3x chlorine cost)

• Slower dissolving: Takes longer to reach full effectiveness

• Incompatibilities: Cannot combine with chlorine or most acidic products

• Harder to test: Some test kits don’t measure bromine accurately

• Persistence: Can build up if not monitored

Best for:

• Spas with heavy use

• Those prioritizing comfort over cost

• Owners with sensitive skin

• Larger spas (economies of scale)

Cost: ~$65 per 5 kg of tablets; typically need 1–3 tablets per week depending on usage

Compatibility:

• Can combine with active oxygen (oxygen reactivates bromine)

• Cannot combine with chlorine

• Cannot combine with PHMB

• Cannot combine with other acidic products

Active Oxygen: The Natural Option

How it works:
Active oxygen (hydrogen peroxide-based) kills microorganisms through oxidation. Unlike chlorine and bromine, it doesn’t create new chemical compounds but simply reverts to water and oxygen.

Forms available:

• Tablets or powder: Usually powdered form

• Liquid: Less common

Advantages:

• Natural: Safe, environmentally friendly

• Non-irritating: No chemical smell or skin irritation

• No residual chemicals: Reverts to water and oxygen

• Combine with bromine: Reactivates bromine for extended effectiveness

• Biodegradable: No lasting environmental impact

• Gentle on equipment: Minimal corrosion

• Cost-effective: Moderate pricing (~$20–$25 per 20 tablets)

Disadvantages:

• Weak on its own: Must combine with persistent sanitizer (chlorine or bromine)

• Temperature sensitive: Effectiveness reduces with heat (need more in hot spas)

• Limited shelf life: Degrades over time once package opened

• Not for shock alone: Requires persistent product for backup disinfection

• Slower acting: Doesn’t immediately kill all contaminants like chlorine

Best for:

• Environmentally conscious spa owners

• Those seeking mild, non-irritating treatment

• Spas combined with bromine system

• Smaller spas with light use

Cost: ~$20–$25 per 20 tablets; typically need 1–2 tablets every 2–3 days (in combination with bromine or chlorine)

Usage approach:

• Weekly: Add persistent sanitizer (chlorine or bromine)

• As needed: Add active oxygen for oxidation

• Shock treatment: Use active oxygen with chlorine for intensive cleaning

Compatibility:

• Can combine with chlorine (especially for shock treatment)

• Can combine with bromine (oxygen reactivates bromine)

• Cannot combine with PHMB

PHMB: The Stable Option

What it is:
PHMB (Polyhexamethylene Biguanide) is a synthetic biocide that kills microorganisms without the characteristics of traditional halogens.

Forms available:

• Liquid: Standard form

Advantages:

• Temperature stable: Works effectively across full spa temperature range

• pH stable: Works across wide pH range

• Non-irritating: Doesn’t irritate skin, eyes, or mucous membranes

• No chemical smell: No strong odors

• Persistent: Stays in water longer than chlorine or bromine

• Gentle on equipment: Minimal corrosion

• Affordable: ~$10–$20 per liter

Disadvantages:

• Doesn’t kill algae: Must use separate algaecide

• Multiple incompatibilities: Cannot combine with chlorine, bromine, copper, or bronze

• Harder to test: Limited test kit availability

• Slower acting: Not as fast as chlorine

• Specialty product: Less widely available than chlorine/bromine

• Buildup risk: Can accumulate if overused

Best for:

• Those seeking non-halogen treatment

• Spas with specific incompatibility concerns

• Owners prioritizing long-lasting stability

• Residential spas with light-to-moderate use

Cost: ~$10–$20 per liter; typically need 1–2 liters for initial treatment and smaller amounts for maintenance

Compatibility:

• Cannot combine with chlorine, bromine, copper, or bronze

• Must use separate algaecide for algae prevention

• Requires compatible test kit

Ozone: The High-Tech System

How it works:
An ozonator produces ozone gas (O₃)—a powerful oxidizer that kills microorganisms. Ozone reverts to oxygen (O₂) after use.

Installation requirements:

• Ozonator unit must be installed in spa system

• Requires continuous filtration for ozonator to work

• Integrates with spa’s circulation system

Advantages:

• Highly effective: Ozone is a powerful oxidizer

• Reduces chemical use: Ozone does heavy lifting; minimal sanitizers needed

• No chemical smell: Eliminates chlorine/bromine odors

• Reduces irritation: Less chemical irritation from fewer sanitizers

• No chemical residue: Ozone reverts to oxygen (no persistent chemicals)

• Environmentally friendly: No lasting chemical byproducts

Disadvantages:

• Expensive initial investment: ~$50–$200 for ozonator unit

• Not standalone: Must still use persistent sanitizer (chlorine, bromine, or PHMB)

• Installation required: May need professional installation

• Ongoing maintenance: Ozonator has lifespan; requires eventual replacement (~5–10 years)

• Electricity requirement: Ozonator runs continuously

• Learning curve: More complex system to understand and manage

Best for:

• Large spas with heavy use

• Those prioritizing comfort and water quality

• Budget-flexible spa owners

• Long-term spa owners

Cost: $50–$200 for unit; plus electricity and occasional replacement ($50–$100 every 5–10 years)

How it works with other products:

• Still requires persistent sanitizer (chlorine, bromine, or PHMB)

• Ozone reduces amount of sanitizer needed (30–50% reduction typical)

• Best combined with minimal chlorine or bromine

Comparison Table: Sanitizer Options

Testing Spa Water: Essential Monitoring

Regular water testing is critical to spa health. You cannot maintain proper chemistry without testing.

What to Test

Essential tests (weekly minimum):

Sanitizer level:

• Chlorine: 1–3 ppm (parts per million)

• Bromine: 2–4 ppm

• PHMB: 30–50 ppm

• Active oxygen: 2–4 ppm (when used with persistent sanitizer)

pH:

• Ideal: 7.2–7.8

• Test at least weekly

Alkalinity:

• Ideal: 80–120 ppm

• Test weekly

Optional but helpful:

Calcium hardness:

• Ideal: 150–250 ppm

• Test monthly

Cyanuric acid (stabilizer):

• Ideal: 25–50 ppm (if using stabilized chlorine)

• Test monthly

Testing Methods

Test strips:

• Cost: $10–$20 per bottle (50–100 strips)

• Ease: Very easy (dip strip, read color)

• Accuracy: Moderate (~80% accurate)

• Best for: Quick weekly checks

Liquid test kit:

• Cost: $25–$50 per kit

• Ease: Moderate (requires mixing reagents, timing reactions)

• Accuracy: High (~95% accurate)

• Best for: Precise monitoring, professional results

Digital testers:

• Cost: $100–$300

• Ease: Very easy (push button, digital readout)

• Accuracy: High (~95% accurate)

• Best for: Frequent testing, convenience

Professional testing:

• Cost: $0–$30 per test

• Ease: Very easy (bring sample to supplier)

• Accuracy: Very high (lab testing)

• Best for: Troubleshooting issues, monthly verification

Testing Schedule

Weekly (minimum):

• Sanitizer level

• pH

• Alkalinity

Every 2 weeks:

• Calcium hardness

Monthly:

• Professional lab test (verification)

As needed:

• Any time water appears cloudy, discolored, or has odor

• Any time you add chemicals

• After heavy use periods

Regular Maintenance Schedule

Daily Tasks

• Visual inspection: Check water clarity, color, smell

• Skimmer cleaning: Remove surface debris

Weekly Tasks (at minimum)

• Test water chemistry (sanitizer, pH, alkalinity)

• Clean filter basket (skimmer and pump)

• Add sanitizer (as needed based on tests)

Bi-Weekly Tasks

• Test calcium hardness

• Brush spa surfaces (prevent algae growth)

• Clean filter cartridge (if pressure high)

Monthly Tasks

• Professional water test (verification)

• Deep clean filter (backwash or rinse)

• Test cyanuric acid level (if using stabilized chlorine)

Seasonal Tasks

Summer (or high-use period):

• Increase testing frequency (twice weekly)

• Increase sanitizer doses

• Clean filter more frequently

• Monitor for algae growth

Winter (or low-use period):

• May reduce testing frequency (keep weekly minimum)

• Reduce sanitizer slightly if needed

• Still run filter regularly

Spring (opening):

• Drain and refill spa

• Clean all surfaces

• Test equipment function

• Balance water before use

Fall (closing):

• Drain spa completely

• Clean thoroughly

• Store cover

• Prepare for off-season

Shock Treatment: Intensive Water Cleaning

Occasionally, spas need shock treatment—a high-dose disinfection.

When to Shock

• After heavy use: Parties, multiple guests

• Visible algae: Green or cloudy water

• Strong chlorine smell: Indicates chlorine byproducts

• Monthly maintenance: Even with proper treatment

• After testing shows low sanitizer: Despite regular dosing

How to Shock

With chlorine:

• Use powder or liquid chlorine

• Dose: 5–10x normal amount (follow product instructions)

• Apply in evening

• Run filter overnight

• Test in morning; swim when sanitizer normal

With active oxygen:

• Use with chlorine (oxygen + chlorine combination)

• Oxygen oxidizes contaminants; chlorine kills microorganisms

• Follow product dosing instructions

• Very effective for intense cleaning

Timeline:

• Apply shock treatment in evening

• Run filter continuously overnight

• Test water in morning

• Usually safe to use next day

Preventing Common Water Problems

Cloudy Water

Causes:

• Insufficient filtration

• Low chlorine/sanitizer

• High pH or alkalinity

• Dead algae or debris

• Calcium scaling

Solutions:

• Run filter longer (8–24 hours)

• Add sanitizer if low

• Test and balance pH/alkalinity

• Shock treatment if algae suspected

• Replace filter if dirty

Green Water

Cause: Algae bloom

Solutions:

• Shock treatment immediately

• Add algaecide if not using chlorine/bromine

• Brush surfaces daily

• Run filter continuously for 24+ hours

• May require multiple treatments

Brown/Black Water

Cause: Severe algae or organic debris

Solutions:

• Drain and refill spa (in severe cases)

• Or intensive shock treatment + continuous filtration

• Clean all surfaces thoroughly

• Replace filter

Strong Chemical Smell

Cause: Chlorine byproducts (chloramines)

Solutions:

• Shock treatment with chlorine

• Reduce chlorine slightly (may be overdosed)

• Increase aeration

• Test pH (adjust if needed)

Equipment Corrosion

Cause: Low pH (acidic water)

Solutions:

• Test and raise pH immediately

• Reduce chlorine (using stabilized chlorine)

• Use alkalinity increaser to buffer pH

• Consider switching to bromine (more pH stable)

Scaling or Crusty Buildup

Cause: High pH, high alkalinity, or high calcium hardness

Solutions:

• Test and lower pH/alkalinity

• Reduce calcium hardness if too high

• Use descaling products

• Prevent by maintaining proper balance

Frequently Asked Questions About Spa Water Treatment

Q1: How often should I change spa water?

A: Depends on usage and maintenance:

Well-maintained spa:

• Every 3–4 months (drain and refill)

• Heavy use might require every 6–8 weeks

• Light use might last 4–6 months

Why drain periodically:

• Accumulated dissolved solids build up over time

• Minerals and salts concentrate

• Cannot be filtered or chemically removed

• Fresh water prevents scaling and corrosion

Signs water needs changing:

• Chemistry impossible to balance

• Persistent cloudy appearance

• Visible scale buildup

• Water smells despite proper treatment

Q2: Can I use pool chlorine in my spa?

A: Generally not recommended.

Why pool chlorine isn’t ideal:

• Different stabilization (pool uses cyanuric acid; spas use different formulations)

• Not formulated for spa conditions (pH sensitivity, heat)

• May cause pH swings in spas

• Can damage spa equipment

Exception:

• Calcium hypochlorite (pool powder) can be used in spas cautiously

• Always use spa-specific chlorine when available

Q3: Can I combine chlorine and bromine?

A: Absolutely not.

Why they’re incompatible:

• Creates harmful chemical reactions

• Reduces effectiveness of both

• Can damage equipment

• Creates unpleasant odors

Important rule:

• Choose one system and stick with it

• If switching, drain spa completely and refill before changing systems

Q4: Is ozone better than chlorine?

A: Both have advantages; choice depends on priorities:

Ozone advantages:

• More powerful oxidizer

• Reduces need for chemicals

• No chemical smell or irritation

• Better for sensitive individuals

Chlorine advantages:

• Much less expensive

• No equipment installation required

• Easier to use and test

• Proven track record

Reality:

• Ozone is “better” in comfort but costs significantly more

• Chlorine is “better” value but less comfortable

• Both work effectively when properly maintained

Q5: How often should I test my spa water?

A: Minimum: weekly

Recommended:

• Twice weekly for heavy use

• Once weekly for normal use

• Three times weekly during problem-solving

Cannot skip testing:

• Water chemistry changes constantly

• Testing is the only way to know actual levels

• Improper chemistry leads to problems

• Regular testing prevents costly issues

Q6: What’s the best product for my spa?

A: Depends on your priorities:

If budget is priority: Chlorine ($20–$25 per week)

If comfort is priority: Bromine ($40–$60 per week) or Ozone ($50–$200 initial + small sanitizer)

If natural/environmental concern: Active oxygen with bromine

If no irritation is priority: Bromine, PHMB, or Ozone

If minimal maintenance is priority: Ozone (though initially expensive)

General recommendation: Start with chlorine if budget-conscious; upgrade to bromine if comfort concerns become important.

Q7: Why is my spa water cloudy despite proper chemistry?

A: Several possibilities:

• Filter too dirty: Cartridge needs cleaning/replacement

• Insufficient filtration time: Run filter longer (8–24 hours)

• Calcium buildup: Water is too hard

• Dead algae: Algae died but debris suspended

• Biofilm: Invisible slime coating surfaces

Solutions:

• Clean/replace filter cartridge

• Run filter 24 hours

• Test calcium hardness

• Shock treatment if algae suspected

• Brush surfaces thoroughly

Q8: Is it safe to use my spa immediately after chemical treatment?

A: Depends on treatment type:

Chlorine:

• Wait until chlorine level reaches normal (below 5 ppm)

• Usually 4–8 hours after normal dosing

• After shock treatment: 12–24 hours

Bromine:

• Wait until bromine below 4 ppm

• Usually 4–8 hours after normal dosing

• After shock treatment: 12–24 hours

Ozone:

• Safe immediately (ozone converts to oxygen)

• No waiting period necessary

Rule: If in doubt, wait overnight or until sanitizer returns to normal.

Q9: Can I treat my spa less frequently to save money?

A: Short-term yes, but not recommended:

What happens:

• Water chemistry becomes unbalanced

• Microorganisms thrive

• Problems develop (algae, cloudy water, equipment damage)

• Fixing problems costs more than prevention

Cost reality:

• Preventative treatment: $10–$30/week

• Shock treatment and equipment repair: $100–$1,000+

• Prevention is always cheaper than treatment

Better budget strategy:

• Use less expensive sanitizer (chlorine vs bromine)

• Test less frequently (weekly vs daily, if minimal use)

• Maintain consistent small doses rather than sporadic large ones

Q10: What should I do if my spa has an algae bloom?

A: Act immediately—algae spreads rapidly:

Step 1: Stop using spa

• Algae can cause infections

• Spa is not safe until treated

Step 2: Test water

• Determine sanitizer and pH levels

Step 3: Shock treatment

• Use appropriate shock (chlorine + oxygen best)

• Dose heavily (follow product instructions)

Step 4: Continuous filtration

• Run filter 24 hours to remove dead algae

Step 5: Brush surfaces

• Brush spa surfaces daily for 2–3 days

• Prevents regrowth

Step 6: Monitor and retreat if needed

• Some algae requires multiple treatments

• Test daily; retreat if algae returns

Prevention going forward:

• Weekly testing prevents algae (catches early growth)

• Proper sanitizer levels prevent algae from starting

• Regular shock treatment prevents buildup

Final Thoughts: Maintaining Pristine Spa Water

Spa water treatment doesn’t have to be complicated or expensive. The key is establishing a consistent routine and sticking with it.

The simple formula:

1. Filter regularly: Run filter 4–8 hours daily minimum

2. Test weekly: Know your water chemistry

3. Treat consistently: Add sanitizer as needed based on tests

4. Balance carefully: Maintain pH and alkalinity in ideal ranges

5. Clean thoroughly: Brush surfaces, clean filter, skim debris

6. Monitor closely: Catch problems early before they escalate

Expected outcomes:

• Crystal-clear water

• No chemical smell or irritation

• No algae or cloudiness

• Healthy, safe spa experience

• Equipment lasting longer

• Lower long-term costs

Start today:

1. Choose your sanitizer system (chlorine easiest to start with)

2. Get a test kit or test strips

3. Establish weekly testing routine

4. Add chemicals as needed based on tests

5. Enjoy your spa knowing it’s clean and safe

Your spa is an investment in your health and relaxation. Maintain it properly, and it will provide years of enjoyment.