Milky Pool Water After Shock Treatment

Introduction

Have you done a shock treatment on your pool and now the water has turned milky or cloudy white? This is one of the most common problems we encounter in pools in Margem Sul, especially during summer when shock treatments are more frequent.

Milky water after shock doesn't necessarily mean something went wrong – in many cases it's a temporary and normal reaction. However, if the cloudiness persists, it may indicate a problem that needs correcting to prevent damage to the pool or discomfort for swimmers.

In this article, we explain the causes of milky water after shock, how to identify the specific source of the problem, solutions for each case, and how to prevent this from happening next time.

What Is Shock Treatment

Definition

Shock treatment (or superchlorination) involves adding a high dose of chlorine or other oxidiser to:

Types of Shock

Normal Process After Shock

After a correct shock treatment:

1. 0-2 hours: Water may become slightly cloudy (normal)
2. 2-6 hours: Cloudiness should start to decrease
3. 6-24 hours: Water should progressively clear
4. 24-48 hours: Water should be crystal clear

Causes of Milky Water

1. Calcium Precipitation

The most common cause in Margem Sul pools:

Signs:

• Uniform whitish water
• White deposits on walls
• Scale at waterline
• pH rose after shock

2. Dead Algae Particles

After killing algae, the remains float in suspension:

Signs:

• Water had algae before shock
• Cloudiness with a tint (not pure white)
• Debris at bottom after settling
• Filter clogs quickly

3. Oxidised Combined Chlorine (Chloramines)

When shock breaks down chloramines:

• Releases compounds that cause temporary cloudiness
• Strong "chlorine" smell (actually chloramines)
• Usually clears in 24-48 hours
• More common in heavily used pools

4. Metal Reaction

Metals in the water oxidise with chlorine:

Signs:

• Well or borehole water
• Old copper piping
• Corroded heater
• Specific colour in cloudiness

5. Insufficient Filtration

The system can't clean out particles:

6. Excess Flocculant/Clarifier

Using too much makes things worse:

• Flocculant forms clumps that won't filter
• Excess clarifier causes cloudiness
• Incompatible products react together

Diagnosis: Identifying the Cause

Visual Test

Chemical Tests

Do these tests to confirm:

Glass Test

Simple diagnostic method:

1. Fill a glass with pool water
2. Let it sit for 24 hours
3. Observe the result:

Solutions by Cause

For Calcium Precipitation

Step 1 - Correct pH:

1. Test current pH
2. If > 7.6, add pH reducer
3. Target: pH 7.2-7.4
4. Wait 4-6 hours and retest

Step 2 - Correct alkalinity:

1. If > 120 ppm, use pH reducer
2. Reduce gradually (max 10 ppm/day)
3. Target: 80-100 ppm

Step 3 - Use sequestrant:

1. Add metal/calcium sequestrant
2. Dose: as per product instructions
3. Helps keep calcium in solution

Step 4 - Filter intensively:

1. Pump 24h/day until clear
2. Clean filter frequently
3. Use clarifier if needed

For Dead Algae

Procedure:

1. Vacuum to waste:

• Set valve to "Waste"
• Vacuum entire floor
• Top up water as needed

1. Brush walls and floor:

• Remove stuck debris
• Focus on corners and steps

1. Add clarifier:

• Normal product dose
• Helps clump fine particles

1. Filter continuously:

• Minimum 24-48 hours
• Clean filter every 8-12 hours

1. If persisting:

• Use flocculant (sand filter only)
• Let settle 8-12 hours
• Vacuum to waste

For Oxidised Chloramines

Solution:

This cloudiness usually resolves on its own:

1. Keep filtration running 24h/day
2. Don't add more chemicals
3. Wait 24-48 hours
4. If persisting, do another shock

For Metals

Procedure:

1. Identify the source:

• Test metals in water
• Check fill water
• Inspect equipment

1. Treat the metals:

• Add specific sequestrant
• High initial dose
• Weekly maintenance dose

1. Remove metals:

• Filter with special media (celite)
• Or use flocculant + vacuum

1. Prevent entry:

• Treat well water before adding
• Replace corroded components
• Maintain correct pH (prevents corrosion)

For Insufficient Filtration

Check and correct:

Improve filtration:

1. Add clarifier (normal dose)
2. Filter 24h/day
3. Clean filter every 8 hours
4. Repeat until clear

For Excess Clarifier/Flocculant

If you used too much:

1. Don't add more products
2. Do long backwash (5 minutes)
3. Dilute: Replace 20-30% of water
4. Filter continuously
5. If not resolving: Vacuum bottom to waste

Quick Resolution Guide

Decision Flowchart

Milky water after shock
         ↓
    Test pH and hardness
         ↓
    ┌────┴────┐
    ↓         ↓
pH > 7.8   pH normal
    ↓         ↓
Calcium    Other problem
precipitation    ↓
    ↓      Was there algae before?
Correct pH  ↓         ↓
+ sequestrant Yes      No
              ↓         ↓
         Dead algae  Check:
              ↓        - Metals
         Vacuum +      - Filtration
         clarifier     - Clarifier

Expected Resolution Time

Products Needed

For Each Type of Problem

Estimated Costs

Prevention

Before Shock

During Shock

• Add product gradually
• Distribute across several points
• Keep pump running
• Don't mix different products
• Respect recommended dosage

After Shock

Choosing Shock Product

When to Call a Professional

You Should Contact If:

• Cloudiness persists more than 72 hours
• Treatments aren't working
• You can't identify the cause
• pH or other parameters impossible to balance
• Water with persistent strange colour
• Recurring problems after each shock

A Professional Can:

• Do complete water analysis
• Identify the exact cause
• Have access to professional products
• Resolve equipment problems
• Avoid errors that make things worse

Frequently Asked Questions

Is it safe to swim in milky water?

It depends on the cause. If it's just cloudiness from particles (dead algae, calcium), it's not dangerous but not recommended – low visibility is a risk. If chlorine is still very high (>5 ppm), wait until it drops. When in doubt, don't get in the water.

How long does it take to clear?

With proper treatment: 24-72 hours in most cases. If it doesn't start clearing within 24 hours, reassess the diagnosis. If still cloudy after 72 hours, there's probably an unidentified problem.

Can I use clarifier and flocculant together?

Not simultaneously. Clarifier groups particles for the filter to capture. Flocculant makes particles sink for vacuuming. Use one or the other. If using flocculant, let it settle and vacuum to waste – don't filter, as flocculant damages the filter.

Did the shock damage my pool?

The milky water itself doesn't cause damage. However, prolonged calcium precipitation can leave deposits on surfaces. If you resolve it quickly (24-48h), there won't be damage. If you leave weeks with precipitated calcium, you may get stains that are hard to remove.

Should I do another shock if the water didn't clear?

Usually no. If the water didn't clear, adding more chlorine probably won't help and may make things worse (especially if it's a calcium problem). First identify and resolve the cause of cloudiness, then retest the water to decide if you need more chlorine.

Conclusion

Milky water after shock treatment is a common problem but usually easy to resolve. The main points to remember are:

• Identify the cause before trying to fix it
• Test pH and hardness – calcium precipitation is very common
• Filter intensively – minimum 24 continuous hours
• Don't add more products without diagnosis
• Prevention is easier – adjust pH before shocking

If you need professional help with your pool in Margem Sul, ManutençãoPiscinas is here to help. Contact us for a no-obligation assessment.