You Simmer Bone Broth for 24 Hours. Are You Concentrating Contaminants Too?

You spent four hours sourcing pasture-raised chicken feet and beef knuckles. You found a farmer who grass-finishes his cattle. You bought high-quality apple cider vinegar to pull minerals from the bones. You set your stock pot to a low simmer before bed.

And then you filled it with tap water.

For most clean eaters, this is the invisible contradiction at the center of every batch-cooking session. You've rebuilt your kitchen around ingredient quality — but the one ingredient present in virtually every dish you make, from broth to rice to steamed vegetables to morning oatmeal, gets no scrutiny at all.

The problem isn't just that tap water contains contaminants. It's that cooking amplifies them.

What Heat Actually Does to Your Tap Water

There's a persistent belief that boiling water makes it safe. For biological contamination — bacteria, parasites, viruses — that's largely true. But the contaminants in modern municipal tap water are mostly chemical, not biological. And heat doesn't fix chemical problems.

What boiling does do is evaporate water. And when the water leaves, most of what was dissolved in it stays behind.

Lead doesn't evaporate. Nitrates don't evaporate. PFAS (per- and polyfluoroalkyl substances, the "forever chemicals" found in most U.S. municipal water supplies) don't evaporate. Chloramine byproducts — trihalomethanes and haloacetic acids, formed when chloramine reacts with organic matter — don't evaporate. If anything, boiling concentrates them by reducing the liquid volume.

A pot of soup that simmers uncovered for an hour and reduces by a third has just concentrated whatever was dissolved in the cooking water by roughly 50%. A bone broth that evaporates steadily over 18–24 hours and loses half its volume? The dissolved contaminants in what remains are now roughly twice as concentrated as they were in the tap water you started with.

This is not a hypothetical. It's basic chemistry.

The Bone Broth Problem Is Particularly Stark

Bone broth has become a staple in clean eating circles for good reason. It provides collagen precursors, gelatin, bioavailable minerals, and compounds like glycine and proline that support joint health, gut lining integrity, and sleep. When made properly from high-quality bones, it's one of the most nutrient-dense foods you can make at home.

It's also one of the most water-intensive cooking processes in a home kitchen.

A typical large batch of bone broth starts with 3–4 gallons of water. It simmers for anywhere from 12 to 48 hours. The final yield might be 2 gallons — sometimes less if you're cooking at higher heat or in an open pot. That's a 33–50% reduction, meaning contaminant concentration can double or more.

The irony runs deep: the same long simmering time that extracts valuable minerals from bones is also extracting maximum concentration from whatever chemistry your tap water contains. You're essentially running a gentle reduction on tap water contaminants alongside your collagen extraction.

And here's the part that's harder to dismiss: bones themselves can leach lead. A 2017 study in Food and Chemical Toxicology found that bone broth made from chicken bones contained measurable lead — primarily from the bones, not the water. Starting with contaminated water adds a second lead source to a broth that already has one.

Rice, Oatmeal, and Anything That Absorbs Liquid

If bone broth is the extreme case, rice is the everyday one.

When you cook white or brown rice, the rice absorbs approximately 1.5–2 cups of water per cup of dry grain. That water doesn't boil off — it goes into the food. Whatever was dissolved in it — nitrates, lead, chlorine byproducts — is now in your rice, at roughly the same concentration it was in the tap water.

There's research specifically on this. A 2020 study published in Science of the Total Environment examined arsenic uptake in rice cooked different ways. Rice cooked using the absorption method (standard rice cooker or stovetop absorption) accumulated significantly more arsenic from contaminated cooking water than rice cooked in excess water that was drained. The takeaway: the absorption cooking method that's most common for rice is also the method that transfers the most contamination from water to food.

The same principle applies to:

• Oatmeal: Rolled oats absorb their entire cooking liquid. Whatever's in that water is in your breakfast.
• Quinoa, farro, barley: Same absorption principle. Cook 1 cup of quinoa in 2 cups of tap water — 2 cups of tap water chemistry goes into what you eat.
• Lentils and beans: Especially relevant if you cook dried legumes from scratch, which requires long simmering in a significant volume of water.
• Polenta and grits: Heavy absorption cooking with prolonged heat contact.

For clean eaters who batch cook grains at the start of the week — a common prep practice — this means several servings of grains cooked in unfiltered tap water, portioned out across every meal.

Steaming Is Safer — But Not Immune

Steaming vegetables is generally considered one of the cleanest cooking methods. You're not submerging food in cooking liquid, so direct water absorption is minimal.

But there's still a mechanism worth understanding. Steam carries volatile compounds — and tap water produces more volatile compounds as it heats. The trihalomethanes formed when chloramine reacts with organic material are volatile, meaning they can be released into steam. Research on chlorination byproducts has found that showering in chlorinated water exposes you to inhalable byproducts from steam; the same principle applies in a smaller way to stovetop steaming.

This isn't the primary concern — direct absorption in bone broth and rice matters far more — but it's worth knowing that "steaming" isn't a complete bypass.

Making Soups, Stocks, and Sauces

After bone broth, the next category that matters most is reduced sauces and concentrated stocks.

If you make a pan sauce by deglazing with water and reducing — you're concentrating. If you make a vegetable stock by simmering scraps in water for an hour — you're concentrating. If you make tomato sauce and add a cup of water to the pot, which simmers down over 45 minutes — you're concentrating.

Clean eaters who cook from scratch are running dozens of these small reduction processes every week. Each one is a small-scale version of the bone broth problem.

The Practical Math: Filtered Water vs. Buying Spring Water

The most common workaround for people who are already thinking about cooking water is buying spring water in gallons. It works — but the cost adds up faster than people realize.

A gallon of spring water at a grocery store runs $1–$2. If you use:

• 2 gallons for a bone broth batch twice a month: $4–$8/month
• 1 gallon per week for cooking grains and soups: $4–$8/month
• ½ gallon per week for oatmeal and everyday cooking: $2–$4/month

That's $10–$20/month conservatively, just for cooking water — not drinking water. Over a year, that's $120–$240. Over three years, $360–$720.

A Berkey Big Berkey — the 2.25-gallon model that's the most common choice for a household — runs around $350. The Black Elements filter pair is rated for 3,000 gallons, which at household cooking-plus-drinking use typically lasts 2–4 years. The math inverts fast: by year two, the Berkey has paid for itself versus buying spring water, and it produces more water than you'd realistically buy in jugs.

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A Practical Cooking Protocol With Filtered Water

Once you have filtered water available, here's how to integrate it into a batch cooking workflow:

Bone broth: Use filtered water for the full volume. No exceptions. Fill the Berkey top chamber overnight before a broth day, and you'll have more than enough ready by morning. Use ACV to pull minerals, same as always — the filtered water actually improves mineral extraction slightly because it doesn't compete with the chemistry of chloramines.

Rice and grains: Swap to filtered water for all absorption cooking. Keep a pitcher of filtered water in the refrigerator for quick access when cooking smaller quantities.

Soups and stocks: Fill the pot with filtered water from the Berkey. For large batches, fill a separate pot or pitcher from the Berkey in advance so it's ready when you need it.

Sauces and braises: For anything you're going to reduce, always use filtered water. The reduction step concentrates whatever you start with — this is where it matters most.

Vegetables: Blanching and boiling in filtered water is ideal. Steaming is lower priority but still a good default once you have the water available.

The Bigger Picture

The clean eating movement has done a thorough job of rethinking cooking oils, protein sources, and ingredient quality. The overlooked variable is the one that's in every pot, every morning, every batch-cooking session — the water.

You've already done the hardest work. You changed how you shop, how you read labels, how you cook. Adding filtered cooking water isn't another overhaul. It's a single equipment swap that closes the most consistent gap in an otherwise careful kitchen.

The bone broth you make with filtered water contains the same collagen, the same minerals, the same glycine. It just doesn't come paired with the concentrated chemistry of 18 hours of simmering tap water.

That's a straightforward upgrade. And unlike most kitchen investments, this one actually gets cheaper over time.

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Last updated: 2026-06-23

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