Why Is My Pool Water Cloudy or Off? 7 Must-Know Pool Chemistry Tips

What’s Happening to My Pool? 7 Chemistry Essentials Every Pool Owner Should Know

•  Is your pool water cloudy, green, or just “off,” even though you’re adding chlorine?
• Are your test strips showing strange results like low pH, high stabilizer, or numbers you don’t understand?

You’re not alone—and this beginner-friendly guide is here to help.

In this article, you’ll learn the 7 key water chemistry factors that every pool owner should understand. We’ll explain what each one does, what causes levels to rise or fall, and what you can do to fix them with simple language, real-life tips, and examples.

By the end, you’ll know exactly what’s happening to your pool and how to balance your water like a pro.

But First: Check Your Filter

Before you dive into chemistry, please make sure your filter is clean and circulating properly.
Even perfect water chemistry won’t matter if your system isn’t moving water efficiently. In older pools, especially, filter systems may be underperforming. If your filter resembles the one pictured here, it’s time for a replacement.

What Is Water Balance—and Why Does It Matter?

Water balance is the state in which your pool water remains safe, clean, and stable for swimmers and pool systems. When your water is properly balanced, it:

• Feels better on your skin

• Allows chlorine to work effectively

• Prevents damage to surfaces and equipment

• Stays clear, comfortable, and easy to manage

Let’s break down the seven essential chemistry factors that keep your pool in balance:

1. pH: The Foundation of Pool Balance

What it is:

pH measures the acidity or alkalinity of your water. The scale ranges from 0 (acidic) to 14 (basic), with a pH of 7.4–7.6 being ideal for pool water. Aim for 7.5 as your target.

Why it matters:
If your pH is off, chlorine won’t work properly—leading to cloudy water, irritation, and higher costs.

What raises pH:

• Splashing, waterfalls, or spa jets (they add air to the water)

• Saltwater systems

• Some chemicals like soda ash

What lowers pH:

• Acid (like muriatic acid or dry acid)

• Stabilized chlorine (like trichlor or tablets)

• CO₂ systems

Quick Tip:
Fix alkalinity first—it makes controlling pH much easier.

2. Total Alkalinity (TA): The pH Bodyguard

What it is: TA stabilizes pH and helps prevent large swings. It’s made mostly of bicarbonate and acts like a buffer.

Good range: 90–110 ppm

What raises TA:

• Adding baking soda (sodium bicarbonate)

• Some types of fill water

What lowers TA:

• Adding acid

• Rain, leaks, or splashing that removes or dilutes the pool water

• Reverse osmosis (RO) filters are typically used for drinking water and are installed between the cold water source and the pool. While adding one of these filters to a pool is generally not discussed or practiced in our industry, it is highly recommended.

3. Calcium Hardness (CH): The Pool’s Bone Strength

What it is: CH measures how much calcium is in your water. Your pool needs some—but not too much.

Good range: 250–400 ppm (depends on your pool surface but let's stick to plaster pools)

What raises CH:

• Adding calcium chloride or cal hypo

• Using hard tap water

• Water "grabbing" calcium from plaster or tile grout if it's unbalanced

What lowers CH:

• Diluting the pool with soft water (like rain)

• RO filtration

• Forcing calcium to form dust and vacuuming it out (last resort)

Watch out for: White scale, cloudy water, or rough surfaces.

4. Cyanuric Acid (CYA): The Chlorine Shield

What it is: CYA (also called a stabilizer or conditioner) protects chlorine from being destroyed by sunlight / UV rays.

Good range: 30–50 ppm

What raises CYA:

• Adding it directly (granular or liquid)

• Using stabilized chlorine (trichlor or dichlor tabs/shock)

What lowers CYA:

• Draining and refilling

• RO filtration (Reverse Osmosis)

• Letting it slowly break down (takes months)

• Special CYA-removing products (some work, some don’t)

Important: Too much CYA weakens chlorine—even when your test says chlorine levels are “good.”

5. Total Dissolved Solids (TDS): The "Everything Left Over"

What it is: TDS includes salts, minerals, and leftover chemicals in your pool, basically the gunk that builds up over time.

Why it matters: High TDS can make water appear cloudy, dull, or unresponsive to treatment, even when test results appear good.

What raises TDS:

• Adding chlorine, salt, calcium, or stabilizer

• Replacing evaporated water with tap water

What lowers TDS:

• Draining and refilling

• RO filtration

•  Ozone, and UV systems (long-term prevention)

Pro Tip: If your water looks dull but everything tests okay—check your TDS.

6. Combined Chlorine (CC): The Used-Up Chlorine

What it is: CC is chlorine that’s already reacted with sweat, ammonia, or contaminants. It’s no longer sanitizing and causes that classic “chlorine smell.”

Good level: 0 ppm (or as close as possible)

What raises CC:

• People peeing or sweating in the pool

• Ammonia-based products (like some algaecides or cleaners)

• Certain tap water sources

What lowers CC:

• Shocking the pool (breakpoint chlorination)

• Using enzymes

• Secondary systems like UV, ozone, or AOP

• RO filtration

Remember, a Strong chlorine smell ≠ means a clean pool. It might mean chlorine is struggling.

7. Phosphates: The Algae Food

What it is: Phosphates are nutrients that feed algae. While they don’t consume chlorine directly, they create conditions that allow chlorine to be used up fighting algae.

What raises phosphates:

• Tap water

• Leaves, grass, dirt

• Pool chemicals (like stain inhibitors)

• Swimmers (yes, humans carry phosphorus too!)

What lowers phosphates:

• Using a phosphate remover

• RO filtration

• Diluting the pool with cleaner water

Tip: Keep levels below 500 ppb to prevent algae growth and help chlorine work efficiently.

Want to stop algae before it starts?

Wrap-Up: A Simple Plan to Keep Your Pool Water in Balance

Balancing pool water may sound complicated at first—but once you know what to look for, it becomes much more manageable.

Here’s the order we recommend when testing and adjusting:

1. Start with Total Alkalinity (TA)

2. Adjust pH

3. Then check Calcium Hardness (CH)

4. Test Chlorine and CYA

5. Keep an eye on Phosphates, TDS, and CC weekly

Final Tips for Every Pool Owner

Now that you understand the 7 pillars of pool water balance, your job is simple:

• Test your water weekly

• Make one small change at a time

• Use this guide to understand what the numbers mean—and what to do next

And remember: If your pool water is balanced, your chlorine can focus on keeping it clean.

Need Help? Watch this video to prevent pool problems.   

Want Expert Help with Water Chemistry?

If your water still feels off or your numbers aren’t adding up, our service division can help. We offer:

• Advanced water testing

• Professional pool balancing

• Tailored recommendations based on your pool system

Let’s get your pool crystal-clear again.