How to Correct Low Alkalinity in Pools

Correcting low alkalinity in your pool is key to keeping the water safe and stable. When alkalinity drops, pH levels become unstable, which can damage surfaces and make the water uncomfortable to swim in. Fixing it is simple once you know what to look for and how to treat it.

What Is Alkalinity and Why Does It Matter?

Total alkalinity is a measure of the water’s ability to resist changes in pH. It acts as a buffer that keeps pH from fluctuating.

The ideal total alkalinity range is 80 to 120 ppm. When alkalinity is too low:

pH levels swing up and down easily
Corrosion may occur in metal parts
Plaster or vinyl surfaces may deteriorate
Swimmers may experience skin and eye irritation

Keeping alkalinity in range makes water care easier and more predictable.

Why Does Pool Alkalinity Drop?

There are a few common reasons why alkalinity drops:

Heavy rainfall diluting the water
Adding too much acid (muriatic or pH reducer)
Refilling with soft or low-alkalinity water
Frequent shocking with certain chlorine types
Evaporation and splash-out changing water balance

Understanding the cause helps prevent it from happening again.

When Should You Test Pool Alkalinity?

You should test alkalinity:

At least once a week
After heavy rain
After adding acid or other chemicals
When opening or closing your pool

Use test strips, liquid drop kits, or a digital tester. Always test alkalinity before adjusting pH since one affects the other.

How to Raise Alkalinity in Your Pool

Step 1: Test Your Current Alkalinity

Start by testing your water with a reliable kit. Write down the alkalinity level and the pH level. If both are low, focus on alkalinity first.

Step 2: Calculate How Much Alkalinity Increaser You Need

Use an online calculator or refer to product packaging. Most alkalinity increasers are sodium bicarbonate (baking soda). As a general rule:

To raise alkalinity by 10 ppm in 10,000 gallons, use 1.5 pounds of baking soda

Step 3: Add Increaser to the Pool

Turn on your pool pump
Broadcast the baking soda around the pool or add to the deep end
Avoid dumping in one spot
Do not add when swimmers are in the water

Let the pump run for several hours to distribute the chemical evenly.

Step 4: Retest and Repeat if Needed

Test alkalinity again after 6 to 12 hours. If the level is still low, repeat the process in small amounts.

Never try to raise alkalinity all at once. Making small adjustments helps avoid overshooting your target and creating high pH levels.

What Happens If Alkalinity Is Too Low?

Low alkalinity affects your pool in many ways:

pH becomes unstable and hard to control
Pool water may become acidic
Heaters and metal parts may corrode
Surfaces may etch or pit
Chlorine becomes less effective

These issues cost more in the long run and make your pool harder to maintain.

What Products Can Help Maintain Alkalinity?

To help keep your alkalinity stable, consider:

Alkalinity increaser (sodium bicarbonate)
pH buffer tablets or pods
Enzyme treatments to reduce organic waste
Pool covers to limit rain dilution and evaporation

Using these products consistently can keep levels from dropping too fast.

Who Should Adjust Pool Alkalinity?

Most pool owners can handle alkalinity adjustments themselves. Just follow label directions and retest regularly.

Call a pool professional if:

Your levels keep dropping unexpectedly
You cannot keep pH stable
You suspect scale or corrosion in the system

An expert can check for deeper water chemistry problems.

How to Keep Alkalinity Stable Long-Term

Test alkalinity weekly
Avoid adding acid and alkalinity products at the same time
Use baking soda as needed to maintain range
Run the pump daily for proper mixing
Keep your pool covered during storms
Monitor pH levels closely

Keeping total alkalinity within range protects your pool and simplifies your chemical routine. With regular testing and care, you can avoid the problems caused by low alkalinity and enjoy clean, comfortable water all season.