This is really, really important for any kind of fermentation (including things like sourdough starter). I believe it's possible to get rid of some kinds of chlorination from municipal water sources by boiling the water first, but it is not possible to get rid of "chloramines," which are widely used (at least in the US). The web page for your local water supplier should be able to tell you whether they use chloramines or not, but I pretty much always just use bottled water that I know has nothing in it that would inhibit the fermentation.
It may be what's used in dechlorinator products, but vitamin C (ascorbic acid, or Sodium Ascorbate) does a good job of converting chloramines (or just chlorine) to salt, NaCl. I used an ascorbic acid shower filter for years when living in a city that used chloramine in their water. It worked well and I could tell every five months or so that it needed to be refilled because my skin started itching from the chlorine.
You can also buy dechlorinator for use with aquariums - super important to not accidentally kill the bacteria maintaining your nitrogen cycle. A bottle goes a very long way (ratio is drops per gallon of tap water).
My sourdough starter is absolutely fine with chloraminated water. I do use bottled water for pickles though because each batch is starting from scratch.