Why Is My Pool’s pH Off? (And How to Fix It)

Ever test your pool water and see that the pH number is way too high… or too low? Please don’t ignore it! When your pool's pH is out of balance, it can disrupt your water chemistry, damage your equipment, irritate your skin, and even reduce the effectiveness of chlorine.

In this post, we’ll break down why pH goes off, what the ideal range is, and how to bring it back into balance.      


🧪 What Is pH, and Why Does It Matter?

pH measures how acidic or basic your pool water is — on a scale from 0 to 14:

• 7.0  is neutral
• Below 7.0  = acidic
• Above 7.0 = basic (or alkaline)

For pool water, the ideal pH range is 7.2 to 7.6.

When pH is too low, your water is acidic — it can corrode metal, damage pool surfaces, and burn your eyes.

When pH is too high, chlorine becomes less effective, water can turn cloudy, and you may get scale buildup or itchy skin.


⚠️ Why Your Pool’s pH Might Be Off

1.   Rainwater      

Rain tends to be acidic, especially after storms. Even small amounts of rain can throw off your pH balance — especially in smaller pools.

2.  Refilling with Tap Water      

Depending on your local water supply, tap water can be naturally high in pH or alkalinity, which raises your pool's pH after top-ups.

3.  Heavy Pool Use      

Swimmers introduce body oils, sweat, sunscreen, and other contaminants that can affect water balance — especially if your pool gets a lot of use.

4.  Chemical Imbalances      

Using other chemicals (like chlorine, algaecides, or shock) without balancing alkalinity first can cause pH levels to spike or crash.

5.  High Alkalinity      

Total alkalinity acts like a “pH buffer” — when it's too high, your pH tends to drift upward. If it’s too low, pH can crash.


🔧 How to Fix Low or High pH in Your Pool

📉 If Your pH Is TOO HIGH (Above 7.6):

• Use a pH reducer (also called pH Down), usually made with muriatic acid or sodium bisulfate
• Always follow label directions based on your pool’s volume
• Add the product with the pump running and let it circulate for at least 4–6 hours
• Re-test and repeat if needed

📝    Pro Tip:    If both pH and alkalinity are high, lower alkalinity first  — it helps bring pH down too.

📈 If Your pH Is TOO LOW (Below 7.2):

• Use a pH increaser (also called pH Up), typically sodium carbonate (aka soda ash)
• Add gradually — too much too fast can spike your pH
• Circulate the water for several hours before re-testing
           

📝  Pro Tip:  Low pH often means low alkalinity too — test and adjust both if needed.


✅ How to Keep pH in Check

• Test your water 2–3 times a week (especially after rain or heavy swimming)
• Maintain total alkalinity between 80–120 ppm to help stabilize pH
• Use a stabilized chlorine product to avoid wild swings
• Shock your pool regularly — but constantly rebalance pH afterward