Water is the second-biggest ingredient in pizza dough, 60 to 75% of the flour’s weight in most recipes, so it attracts a lot of worry: filtered or tap, whether chlorine harms the yeast, whether hard water toughens the dough. The most thorough answer comes from Modernist Pizza, whose team tested it directly. The results below are theirs; this site hasn’t repeated the test.
What Modernist Pizza tested
The team made each of their master doughs (Neapolitan, New York, artisan, high-hydration al taglio, Detroit, focaccia and New York square) with five kinds of water, baking more than 100 pizzas in all.
| Water | What it was | Result |
|---|---|---|
| Tap | Ordinary municipal water, with low levels of chlorine and fluoride | Consistently preferred |
| Filtered | Tap water through a filter | Only subtle differences from tap |
| Distilled | Water with the dissolved solids removed | Only subtle differences from tap |
| Hard mineral | Gerolsteiner, 2,488 ppm total dissolved solids | Lower volume in bread-like pizzas, with a denser crumb and more chew |
| Heavily chlorinated | Deionized water chlorinated to 4 ppm, which the book gives as the legal limit for tap water | No difference in how the dough behaved |
Their conclusion: across the board there were only subtle differences in taste and volume, the type of water doesn’t make for a better pizza, and buying filtered or distilled water isn’t worth it unless your supply smells foul or has some other major contaminant. The book’s rule is short: if you can drink it, you can use it in your dough, and if it looks murky or smells odd, don’t.
The chlorinated water surprised them. They expected it to suppress the yeast, but the dough behaved no differently, and the Neapolitan pizza made with it had excellent volume, good leoparding and extra crispness. Their reasoning is that chlorine and fluoride evaporate readily on contact with air, so little may be left after mixing; that the yeasts and bacteria in starters and commercial yeast have been selected to tolerate them; and that no chlorine remains in the dough after baking.
Chlorine and chloramine
So chlorine at tap-water levels isn’t a problem for pizza dough, even at the legal maximum. One gap: many utilities now disinfect with chloramine, a longer-lasting compound made by adding ammonia to chlorine, and the EPA says more than one in five Americans drink chloraminated water. Modernist Pizza tested chlorine, not chloramine, so its result doesn’t cover that case directly. If your water tastes and smells fine, the drinkability rule still applies.
Hard water
The usual warning is that hard water, rich in calcium and magnesium, toughens dough. Modernist Pizza found doughs made with hard water virtually indistinguishable from those made with filtered water. The exception was their very hard mineral water, at 2,488 ppm of dissolved solids, which consistently cost bread-like pizzas some volume. For scale, the EPA’s guideline for dissolved solids in drinking water is 500 mg/L, a fifth of that; above it, water may taste salty and leave deposits.
If you want to check yours:
- Read your utility’s annual water quality report, or ask the utility for a full analysis.
- Use a TDS meter. Modernist Pizza points out that these cheap meters estimate dissolved solids from conductivity, and that very hard water, which reads high, can also taste off.
If your water is very hard and your pan pizzas or other bread-like crusts keep coming out dense, make one batch with distilled water and compare. Don’t count on a carbon filter: Modernist Pizza notes that carbon filtration removes chlorine but doesn’t soften water. Softening takes an ion-exchange filter, the kind usually called a water softener.
pH
pH measures how acidic or alkaline water is, on a scale where pure water is a neutral 7. The EPA’s guideline for drinking water is 6.5 to 8.5, a range set for taste and plumbing rather than health. Modernist Pizza’s experiment didn’t isolate pH, but it covered ordinary municipal water, and its conclusion applies: water that’s fine to drink is fine for dough. Inexpensive kits will tell you your water’s pH if you’re curious.
What does matter: how much and how warm
Modernist Pizza sums it up in one line: the type of water doesn’t matter, but the hydration does. How much water you add sets how the dough handles and bakes; the hydration guide covers it by style.
The other thing that matters is temperature. Ken Forkish treats time and temperature as ingredients: warmer dough in a warmer room ferments faster. His approach:
- Aim for a dough temperature. For his slow, low-yeast doughs he gets the best results when the dough is 80 to 82°F (27 to 28°C) after mixing, which he reaches with about 90°F (32°C) water and room-temperature flour in a 70°F (21°C) kitchen.
- Measure it. Use a probe thermometer on the water and on the dough once it’s mixed, and adjust the water warmer or cooler next time.
- Don’t use hotter water than the recipe asks for. For mixing or rehydrating yeast, follow your recipe and the instructions for the yeast you actually use.
- Adjust for the season. In a hot, humid summer kitchen he suggests water 10 to 15°F (5 to 8°C) colder and a dough in the low 70s°F (low 20s°C), or less yeast. In a cold kitchen, start warmer or allow more time.
Modernist Pizza agrees on where control belongs: if you need to speed up or slow down fermentation, change the yeast or the dough temperature. The desired dough temperature formula shows how to calculate the water temperature for your kitchen.
Sources
- Nathan Myhrvold and Francisco Migoya, Modernist Pizza (2021), volume 1, pages 288–291 (water’s role, water quality and purity, and the water experiment) and 314 (controlling fermentation with yeast and temperature).
- Ken Forkish, The Elements of Pizza (2016), chapter 3: Detail 2 (time and temperature) and Detail 5 (adjusting for season and climate).
- US Environmental Protection Agency: “Secondary Drinking Water Standards: Guidance for Nuisance Chemicals” and “Chloramines in Drinking Water.”