Water Quality and Its Impact on Fermentation

I learned this the hard way when my once-lively starter suddenly lost its vigor after moving to a new city. My usual bubbly fermentation turned sluggish, and my loaves lacked their characteristic rise and depth of flavor.

The culprit?

My tap water. What I had brushed off as a minor factor turned out to be a game-changer.

Water affects every aspect of sourdough baking, from yeast activity to gluten development. Whether it's chlorine interfering with microbial life, mineral content influencing dough strength, or hydration levels adjusting to different climates, getting your water right can make or break your bake. Let’s dive in.

Chlorinated vs. Filtered Water: Why It Matters

The Invisible Saboteur: Chlorine’s Impact on Fermentation

Most municipal water supplies contain chlorine or chloramines—chemical disinfectants designed to kill harmful bacteria. While great for making water safe to drink, they’re terrible for sourdough.

Your starter is a thriving ecosystem of wild yeast and lactic acid bacteria, both of which are sensitive to chlorine. When exposed to chlorinated water, fermentation slows down, yeast struggles to reproduce, and your starter can become sluggish or even inactive over time.

Ever had a starter that suddenly stops bubbling despite regular feedings? Your tap water might be the reason.

Filtered Water: The Key to a Healthy Starter

So, what’s the solution? Removing chlorine is easier than you think:

1. Let It Sit – Pour tap water into an open container and leave it uncovered for 12-24 hours. The chlorine will naturally evaporate.
2. Boiling Method – Bring water to a boil and let it cool completely. This helps eliminate chlorine, though it won’t remove chloramines (a more stable disinfectant used in some water systems).
3. Carbon Filters – A simple water filter (like a Brita pitcher) effectively removes chlorine and improves taste.
4. Spring or Bottled Water – When in doubt, use a high-quality bottled water with minimal processing.

The difference is noticeable—filtered water can breathe new life into a sluggish starter, improving fermentation strength and bread flavor.

Adjusting Hydration for Different Climates

Why Climate Affects Hydration

Ever followed a sourdough recipe to the letter, only to find your dough way too wet or too dry? That’s because hydration needs vary based on humidity, altitude, and temperature.

Flour is hygroscopic, meaning it absorbs moisture from the air. In humid climates, flour naturally retains more water, making dough stickier. In dry climates, it soaks up more liquid, leading to stiffer doughs.

The trick is learning to adapt hydration rather than blindly following a recipe’s water-to-flour ratio.

Baking in a Humid Climate

• Use Less Water – Reduce hydration slightly (e.g., drop from 75% to 70%) to compensate for the extra moisture in the air.
• Stronger Gluten Development – Higher humidity can weaken gluten. Try additional stretch-and-folds to strengthen the dough structure.
• Control Fermentation Speed – Warm, humid environments speed up fermentation, so consider refrigerating the dough earlier to prevent overproofing.

Baking in a Dry Climate

• Increase Hydration – Dough dries out faster, so bump hydration up by a few percentage points. Adding just 5-10g of extra water per 500g of flour can make a big difference.
• Cover Dough Well – Use damp towels or airtight containers to prevent skin formation. A light misting of water before covering helps retain moisture.
• Longer Autolyse – Letting the dough rest with water before mixing improves hydration absorption and elasticity.

Whether you’re baking in a steamy coastal town or a dry mountain city, tweaking hydration ensures your dough remains supple, responsive, and easy to work with.

Testing Your Water Quality

If you’re unsure about the quality of your water, simple tests can help:

• pH Strips: A pH level of 6-8 is ideal for fermentation. Highly acidic or alkaline water can impact dough behavior.
• TDS Meters: Total Dissolved Solids (TDS) meters measure mineral content. Moderate mineral content (100-300 ppm) is beneficial for yeast activity.
• Local Water Reports: Most municipalities provide water quality reports online, detailing chlorine, fluoride, and mineral levels.
• DIY Water Kits: Home water testing kits can check for chlorine, fluoride, pH, and heavy metals.

Water might seem like a simple ingredient, but in sourdough baking, it’s a quiet powerhouse. Treat it right, and your bread will thank you with better rise, flavor, and texture.

This article is part of the "Mastering Traditional Sourdough Baking" series.