Does Tap Water Affect Sourdough Baking?

A quick answer: yes, it can. Chlorine, Chloramine, it's all in the water.

Most of the time tap water is fine. If you are using a really good flour for your starter like our go-to Mulino Marino Type 00 Soffiata, but your sourdough starter isn’t bubbling as expected or your dough feels sluggish, your tap water might be part of the problem. Many UK water supplies contain chlorine or chloramine – both are safe to drink, but less friendly to the wild yeasts and bacteria in your dough.

Years ago when indulging in homebrew the local chemist told me to avoid using the water on a Friday as it could have the whole weekend's dose of chlorine in there, so assuming that she wasn't trying to put me off brewing my own, we know that the disinfectant treatment in water can vary - and nowadays, the exact chemical being used can too.

Luckily, it’s easy to work around.

 

So, what’s in your water?

Most UK tap water is treated with chlorine, chloramine or sometimes both:

Chlorine

  • It’s been used for over a century to disinfect water.
  • If you leave tap water uncovered for 24–48 hours, chlorine will naturally evaporate.
  • You can speed this up by boiling or using a filter jug.

Chloramine - A modern alternative to chlorine – more stable and longer lasting.

  • Unlike chlorine, chloramine doesn’t evaporate easily, even if left standing.
  • It requires a special filter (like catalytic carbon) or a Campden tablet (commonly used in home brewing) to remove.

Why does this matter for baking?

Wild yeasts and bacteria – the kind that power your sourdough starter – are sensitive to disinfectants. Even small amounts can:

  • Slow down or stall fermentation
  • Affect the flavour and texture of your bread
  • Interfere with your starter’s natural rhythm

What you can do for your tap water

  • Let it stand uncovered overnight (this removes chlorine, not chloramine)
  • Add a pinch of Campden tablet, it removes both chlorine (instantly) and chloramine (in a few minutes) - about 1/4 tablet for 5 litres of water.
  • You could check your local water supplier’s website to see which they use so you'll know if leaving the water to stand is an option.

Final thought

Water is often overlooked in baking, but it’s one of your most important ingredients – especially in sourdough. A small adjustment can mean the difference between a flat dough and a beautifully open crumb.