There’s a unique peace that comes with looking at your pool in the winter. The water is still, the cover is on, and for a moment, everything seems perfectly maintained. That is, until you do a routine water test and discover your pH levels have plummeted. Low pH is a common but serious winter woe, and addressing it is crucial to prevent long-term damage to your pool’s surfaces and equipment. As the colder months of 2025 approach, understanding How to Raise pH Level in Pool: Best Methods & Ideas (Winter 2025) becomes an essential skill for any pool owner who wants to avoid a costly springtime surprise.
You might be wondering why pH matters so much when the pool isn’t in use. Acidic water, indicated by a low pH reading (below 7.2), doesn’t take a season off. It remains actively corrosive, slowly eating away at metal components like ladders, heaters, and pump seals. It can also etch and degrade plaster finishes and even cause vinyl liners to become brittle. Winterizing your pool isn’t just about adding algaecide and covering it up; it’s about creating a chemically balanced environment that can sit for months without causing harm. This guide will walk you through the safest and most effective ways to correct your water’s chemistry during the chilly season.
Why Your Pool’s pH Drops in the Winter
Before you start adding chemicals, it helps to know why this is happening. The causes of low pH in winter are often different from those in the summer. One of the biggest culprits is the cover itself. While it keeps out leaves and debris, it also traps gases. As organic matter breaks down or as the water chemistry naturally shifts, carbon dioxide can build up under the cover. When CO2 dissolves in water, it forms carbonic acid, which directly lowers the pH level.
Heavy rainfall and melting snow are another major factor. Rainwater is naturally soft and acidic, with a pH typically around 5.6. A significant amount of precipitation entering your pool will dilute the alkaline substances that help buffer the pH, causing a sharp drop. Furthermore, the lack of regular water circulation and the fact that you’re not adding fresh water or shocking the pool as frequently can allow these acidic conditions to take hold and persist.
Your Step-by-Step Guide on How to Raise pH Level in Pool: Best Methods & Ideas (Winter 2025)
Raising pH in the winter requires a gentle and methodical approach. The goal is to make a precise adjustment without overshooting, as you won’t be there to monitor it daily. Your two best chemical choices for this task are soda ash (sodium carbonate) and aeration.
Method 1: Using Soda Ash for a Direct Correction
Soda ash is the most common and effective chemical for raising pH with minimal impact on total alkalinity. Here’s how to use it safely in winter:
- Test Accurately: Use a reliable test kit or test strips to get your current pH and total alkalinity readings. This is non-negotiable.
- Calculate the Dose: Refer to the manufacturer’s instructions on your soda ash container. It will provide a chart showing how much to add per 10,000 gallons of water to raise the pH by a certain amount. Since it’s winter, be conservative. Aim to raise the pH to the lower end of the ideal range (7.2-7.6), perhaps to 7.4.
- Pre-dissolve the Chemical: This is a critical winter step. Fill a large, clean plastic bucket with warm water from inside your house. Slowly add the measured amount of soda ash to the bucket while stirring continuously. Never add dry chemicals directly to the pool, especially in winter, as they can sink to the bottom and bleach or stain the surface.
- Add the Solution: With your pool pump running to ensure good circulation, slowly pour the dissolved soda ash solution into the pool, walking around the perimeter to distribute it evenly.
- Re-test and Wait: Let the pump run for at least 4-6 hours, then retest the pH. It may take longer than usual for the reading to stabilize in cold water. Avoid the temptation to add more chemicals immediately.
Method 2: The Gentle Power of Aeration
If your pH is only slightly low and your total alkalinity is in the correct range (80-120 ppm), aeration is a brilliant, chemical-free method. Aeration works by driving off the excess carbon dioxide (the acidic gas) from the water, which causes the pH to rise naturally. The beauty of this method is that it cannot raise the pH above 8.2, so there’s no risk of overshooting. In winter, you can create aeration by:
- Pointing your return jets upwards so they break the water’s surface.
- If safe and feasible, running any water features like fountains or waterfalls.
- Using an air compressor or a small pond aerator near the steps.
While aeration is slower than adding soda ash, it is the safest long-term strategy for maintaining a stable pH.
Special Winter Considerations for a Safe Balance
Winter pool care has its own set of rules. The cold water significantly slows down chemical reactions, meaning everything takes longer. Be patient after adding soda ash; wait a full 24 hours before considering a second dose. Always ensure your pool pump runs for a full 24-hour cycle after adding any chemicals to ensure they are completely mixed throughout the entire body of water.
It’s also vital to remember the relationship between pH and total alkalinity. Total alkalinity acts as a buffer for pH. If your alkalinity is also low (below 80 ppm), you will find it nearly impossible to stabilize your pH. In this case, you should first raise the total alkalinity using sodium bicarbonate (baking soda), which will also cause a slight rise in pH. Once the alkalinity is corrected, you can then reassess the pH and use soda ash or aeration to fine-tune it.
Preventing Low pH Before Winter Sets In
The best cure is often prevention. The most important thing you can do to avoid winter pH problems is to perform a complete set of water tests right before you close the pool. Don’t just shock it and cover it. Ensure that all levels—pH, alkalinity, calcium hardness, and sanitizer—are perfectly balanced. Starting the winter with ideal chemistry gives you a huge head start and creates a much more stable environment that can withstand the challenges of rain, snow, and trapped gases.
By taking a proactive and informed approach, you can confidently manage your pool’s pH throughout the winter of 2025. A little attention during the off-season ensures that when the warm weather returns, your pool will be ready for a quick and trouble-free opening, preserving your investment and your peace of mind.