What Is Alkalinity in a Pool? (And Why It’s More Important Than You Think)

When it comes to pool chemistry, most people focus on pH and chlorine — but total alkalinity is the behind-the-scenes hero that keeps everything stable.

If your pool water feels like it’s constantly out of balance (especially pH), chances are your alkalinity is to blame.

Let’s break it down:

• What is total alkalinity?
• Why is it important?

How do you fix it when it’s too high or too low?      

🧪 What Is Total Alkalinity?

Total alkalinity refers to the amount of alkaline substances (mainly bicarbonates) in your pool water. These compounds act as a buffer, helping to stabilize your pH levels.

In simple terms:

> Alkalinity keeps your pH from swinging up and down.      

When your alkalinity is in the right range, your pH stays steady — which makes chlorine more effective and your pool easier to maintain.


 ✅ Ideal Alkalinity Levels for Pools

For most pools, you want your total alkalinity to be between:

• 80–120 parts per million (ppm)   

This range keeps your water balanced, your equipment protected, and your swimmers happy.

⚠️ What Happens If Alkalinity Is Off?

 ❌ Low Alkalinity (< 80 ppm):

• Causes pH to fluctuate wildly
• Increases the risk of corrosion to pool equipment, liners, and metal surfaces
• It can cause itchy eyes and skin irritation
• May lead to pool surface staining or etching

❌ High Alkalinity (> 120 ppm):

• Makes it hard to adjust or lower pH
• Leads to cloudy water
• Can cause scale buildup on surfaces and equipment

Reduces chlorine effectiveness

🔧 How to Fix Alkalinity in a Pool

📈 If Alkalinity Is Too Low:

You’ll need to raise it using sodium bicarbonate (aka baking soda or alkalinity increaser).

How much to add?

    Add one and a half lbs of baking soda per 10,000 gallons to raise alkalinity by about 10 ppm.

Steps:      

1. Test your water to confirm low alkalinity
2. Calculate the correct dose
3. Add slowly to the deep end with the pump running
4. Circulate for several hours
5. Re-test and adjust again if needed

📉 If Alkalinity Is Too High:

You’ll need to lower it using muriatic acid or dry acid (sodium bisulfate)

Steps:      

1. Turn off the pump
2. Pour the acid in one spot near a return jet
3. Let it sit for 30–60 minutes (this targets alkalinity more than pH)
4. Turn the pump back on and circulate for several hours
5. Re-test and repeat as needed

📝    Tip: Lowering alkalinity often lowers pH, so be prepared to adjust pH afterward with soda ash or aeration.


🔁 How to Maintain Proper Alkalinity

✅ Test total alkalinity weekly, especially during peak season
✅ Balance alkalinity before adjusting pH      
✅ Keep an eye on alkalinity after heavy rain, refilling, or shocking
✅ Use a pool calculator or consult your local pool store to dose chemicals properly


 💬 Final Thoughts

Think of alkalinity as your pool’s pH bodyguard. When it’s in the right range, everything else is easier to manage — and your water stays clearer, more comfortable, and better for your pool system.

So next time your pH is bouncing all over the place or your water turns cloudy, don’t just throw in more chlorine — check your alkalinity first.

Need help balancing your pool water?  We offer free water testing, professional advice, and all the products you need to keep your pool perfect. Stop by or call us — we’re always happy to help!