How to Fix High Alkalinity in a Pool (Even When pH Is Low)

Why High Alkalinity Matters

High alkalinity is one of the most common pool chemistry problems. When alkalinity is too high, your pH becomes unstable and drifts upward quickly, making it hard to keep your water balanced. If left untreated, high alkalinity can lead to cloudy water, scale buildup, poor chlorine performance, and frustrated pool owners.

Things get even more confusing when alkalinity is high but pH is low—a combination that seems impossible but happens more often than you’d think. The solution requires a very specific sequence. This guide explains exactly how to fix high alkalinity safely, quickly, and correctly.

Step 1: Test Your Water

Accurate chemistry readings matter when dealing with alkalinity and pH.

Ideal Ranges:

Total Alkalinity: 80–120 ppm
pH: 7.1–7.7

If your alkalinity is above 120 ppm and your pH is below 7.1, follow the steps below.

Bring a water sample to Mock Pools & Ponds for a free computerized test if you want exact readings before adjusting chemicals.

Step 2: Raise the pH Without Raising the Alkalinity

To lower alkalinity later, your pH must be in a safe range first.
However—this is critical—you shouldn’t use Splash pH Plus to raise pH because it can raise alkalinity even higher. If aeration is not an option, Splash pH Plus can be used sparingly with frequent testing.

The only way to raise pH WITHOUT raising alkalinity is:

✔ Aeration

This naturally increases pH by releasing carbonic acid from the water.

Easy ways to aerate your pool:

Point return jets upward to break the surface
Run waterfalls, spillovers, or fountains
Use a fountain attachment on a return line
Turn on spa spillover mode
Add an air stone (temporary)
Encourage splashing (no joke — it works)

Important:

Keep circulating the pool during this process. Aeration can raise pH within hours or may take a day depending on pool size and airflow.

Step 3: Once pH Reaches 7.2–7.4, Lower Alkalinity With Acid

Now that pH is in the safe zone, you can safely lower alkalinity.

Use:

Splash pH Minus
or
Muriatic acid

How to lower alkalinity step-by-step:

1. Leave pool pump ON.

2. Mix recommended dose of acid into a bucket of pool water.

3. Pour along pool edge.

4. Allow acid to circulate for 3-4 hours.

Step 4: Retest and Repeat if Needed

Depending on how high your alkalinity started, you may need to repeat:

Aerate → Raise pH
Add Acid → Lower Alkalinity

Repeat these steps until alkalinity falls to 80–120 ppm.

This cycle is normal and can take more than one treatment for heavily imbalanced water.

Step 5: Balance the Water

Once alkalinity is in range, your pH should become much more stable and easier to maintain.

The goal:

pH between 7.4–7.6
Alkalinity between 80–120 ppm

At this point, your water is ready for normal maintenance and sanitizer efficiency improves dramatically.

What Causes High Alkalinity?

Understanding the cause helps prevent it from happening again.

Common triggers include:

Using too much pH increaser
Well water with naturally high alkalinity
Certain types of chlorine (especially cal-hypo)
Overuse of aeration features
Adding baking soda
High dissolved solids

Managing alkalinity weekly prevents big swings in pH.

Symptoms of High Alkalinity

You may notice one or more of these issues:

pH rises quickly after you adjust it
Cloudy or dull water
Scaling on tile or equipment
Irritated eyes and dry skin
Ineffective chlorine
Frequent need for acid additions

Fixing alkalinity restores stability and clarity to your water.

Common Mistakes to Avoid

Using pH increaser — raises alkalinity further
Adding too much acid at once
Trying to fix alkalinity before raising pH
Turning off circulation after adding chemicals
Using household chemicals like vinegar or baking soda (not accurate or safe)

Small errors can create bigger chemistry problems—slow and steady adjustments are best.

When to Call a Professional

You may need help if:

Your alkalinity won’t drop after several treatments
pH rises rapidly every day
Water stays cloudy even after balancing
You’re unsure how much acid to add
You prefer exact dosing recommendations

The experts at Mock Pools & Ponds can test your water, evaluate the cause of the imbalance, and give you a precise treatment plan.

Conclusion: Stabilize Your Water With the Right Process

Fixing high alkalinity when pH is low requires a unique approach:

Aerate to raise pH
Add acid to lower alkalinity
Repeat until stable

Once alkalinity is under control, your pH becomes easier to manage, chlorine works better, and your water stays cleaner and clearer.

For help balancing your pool water, stop by Mock Pools & Ponds. We proudly serve homeowners in Canton, Akron, and Northeast Ohio with free water testing and expert pool care solutions.